A quasi-experimental design was used in an investigation directed at determining whether laboratory time in microbiology would be more efficiently and effectively utilized if scheduled as semi-weekly sessions of 1.5 hours each rather than as a single 3-hour session. Efficiency was measured by the number of procedural and data errors made by students and the amount of time actually spent in lab. Learning outcomes, scores on an epidemic problem-solving assignment, and mean laboratory examination scores were used to denote effectiveness. Subjects consisted of two intact laboratory groups with 24 students in each group. Significant differences were noted between the two groups. Students in the semi-weekly section spend 18.3 percent more time in the laboratory, made 4.4 percent fewer procedural errors, 5.6 percent fewer data errors, and had 10.3 percent higher mean laboratory examination scores. However, no significant difference was noted for the epidemic problem set. It was recommended that serious consideration be given to offering additional microbiology laboratory sections on a semi-weekly basis as a method for improving management of the learning environment. It was also recommended that a similar study be conducted with students enrolled in anatomy. (Author/JN)