During the eighties the following chapters were added to the Society. Beta Zeta Chapter was installed at Cabrini College, Radnor, Pennsylvania, in November of 1981.In 1983, Beta Theta Chapter was installed at Belhaven College in Jackson, Mississippi and Beta Iota Chapter was installed at Bethel College in St. Paul Minnesota.Beta Eta Chapter was installed at Evangel College in Springfield, Missouri in 1985.

         During the nineties, the following chapters have been added to the Society:  Beta Kappa Chapter at Kentucky Wesleyan College, Owensboro, Kentucky, in 1991; Beta Lambda Chapter at Messiah College, Grantham, Pennsylvania in 1993;  Beta Mu Chapter at Costal Carolina University, Conway, South Carolina in 1994.; Beta Delta Chapter at Gwynedd-Mercy College, Gwynedd Valley, Pennsylvania in 1996. Beta Nu was installed at Houghton College, Houghton, New York in 1997.

Beta Xi was installed at Pikeville, College, Pikeville, Kentucky in 1999

         Sigma Zeta had reasons to be optimistic while at the same time having cause for concern through the 1980s and 1990s.  There was a substantial decline in the number of members from 1977 to 1988.  This decline was thought to be due to competition from other organizations on campuses and a significant decline in the number of science majors on most college campuses.  Despite this decline in individual memberships, 10 new chapters were added to the national roster and by 1999 there were 50 recognized chapters still in existence.  In one unusual occurrence, Alpha Tau chapter became inactive when its host school, Annhurst College closed at the end of the 1979-1980 academic year.

         Two of the new chapters, Beta Iota (established in 1983 at Bethel College in St. Paul, Minnesota) and Beta Lambda (established in 1993 at Messiah College in Grantham, Pennsylvania) have been active at the national level since their induction.  Both chapters have hosted National Conventions and  regularly send students and advisors to the conventions.  Nearly every convention has had presenters from these schools since the formation of their chapters.

         A number of efforts were made at the national level to increase the level of participation at National Conventions and to encourage chapters to become more active nationally.  These included adding a student representative to the list of national officers, allowing the publication of peer-reviewed student papers in the Sigma Zetan, changing duties (and titles) of some national officers, and extensive efforts on the part of national officers to contact inactive chapters and potential sites for new chapters.

         At the 1983 Convention, a pilot project was initiated in which a National Student Representative was elected to infuse fresh "plans, ideas, etc." into the national organization.  The first student to hold this position was Rick Merrin of Alpha Gamma (Malone University, Canton, Ohio).  He was replaced by Bruce Hoffman of Mu (Mankato State University, Mankato, Minnesota).  This position was discontinued in 1985.

         Attendees at the 1989 Convention agreed to accept up to three refereed student papers for inclusion in the Sigma Zetan.  The first such paper, authored by Stephen D. Ebbs of Beta (McKendree College, Lebanon, Illinois), was published in 1990.  Despite the value of this opportunity for students, only two other papers were published by 1999.

         In 1998 the National Editor position was replaced by the Publicist.  The Publicist's duties were similar to those of the Editor and also included maintenance of the national web site.  The National Recorder-Treasurer was replaced by the Executive Director whose responsibilities included day-to-day business matters of the organization and communication with local chapters through various reports.  The first Executive Director was Harold Wilkinson (Pi Chapter, Millikin University).

         Sigma Zeta lost a number of people during these two decades who had been active at both local and national levels.  Kenneth Cook (Upsilon, Anderson University) was honored in 1984 for his work as National Recorder-Treasurer, a position he held from 1966 to 1982.  George Welker (Xi, Ball State University) finished his 10-year run as National Editor at the 1985 Convention.  He had served Sigma Zeta in various capacities for 35 years and was given a special Honor Award at the 1985 Convention.  Two national officers announced their retirement from teaching at the 1993 Convention—Ted Platt (Alpha Psi, Hillsdale College) had served 10 years as National Editor and David Dautenhahn (Chi, Missouri Valley College) had been a dedicated Historian for many years.

         A number of historically interesting things occurred at the national level during the 1980s and 1990s.  In 1979 the national dues were $6 and by 1999 they had risen to $25.  At the 1981 Convention, President Joe Sheldon (then at Eastern College and later at Messiah College where he started Beta Lambda Chapter) gave a slide presentation on the eruption of Mount St. Helen's.  One of the student papers presented at the 1985 Convention was by Glenn McQuaide of Alpha Beta (Campbellsville University). He later became a faculty member at Campbellsville and served as a national officer in Sigma Zeta for a number of years.  The historic gavel was lost sometime between the 1985 and 1986 conventions and was not found until just prior to the 1992 meeting.  The 1989 edition of the Sigma Zetan was the first to be generated entirely by computer.  Medallions were available for purchase for the first time at the 1994 Convention.  At both the 1983 and 1993 conventions, attendance was impacted by blizzards.  A national web site was seriously considered for the first time at the 1997 Convention.

         It is obvious that the 1980s and 1990s were decades of change for Sigma Zeta on a national level.  Membership was a concern, though efforts by a number of officers kept the organization healthy and led to the induction of new chapters and active faculty in many locations.  The advent of personal computing and the Internet began to have an impact on interactions between the national office and local chapters beginning in the late 1980s and had become crucial to a number of activities by the end of the 1990s.  And though many long-time advocates and servants of Sigma Zeta retired and were no longer active in the organization, a number of new faculty began to fill their shoes and to lead Sigma Zeta into the new millennium.