Students in a junior college microbiology course were randomly assigned to one of two laboratory treatments: one using radiotracer techniques to investigate aspects of microbial metabolism, and the other using conventional techniques to investigate the same metabolic features. An achievement test administered at the completion of the unit and six weeks later and a laboratory skills test favored the group using radiotracers. The differences were statistically significant. There were no relationships between the effectiveness of the radiotracer technique and student intelligence, science aptitude, or previous science laboratory experience. (Author/AL)