The use of STS vignettes with class discussions is a popular way for science teachers to integrate STS in science courses. Two studies were conducted to test the effects of infusing short STS vignettes with periodic class discussions into the genetics unit of high school biology, on students' awareness of current STS issues, the importance students assign to current STS issues, and their achievement in the genetics unit. The nonequivalent control-group quasiexperimental design was employed in each study, with the frequency with which the vignettes and discussions were used during a six-week period differing across them. In neither study were the control groups exposed to the STS vignettes and discussions. The data did not allow the three null hypotheses to be rejected in either experiment. Recommendations are made on the use of STS vignettes by science teachers, and for further research.