Background: Problem-based learning is a student-centred, problem-based, small-group method of learning that emphasizes use of scenarios. The objective of this comparative descriptive study was to determine the difference in cognitive domain scores after lecture-based learning and problem-based learning.Methods: This comparative descriptive study was conducted at a municipal medical college in Thane, Maharashtra, India. After approvals, the study was explained to third-year MBBS students and written informed consent was obtained from willing students. After delivering lectures on five topics in environmental health in the subject of Community Medicine, a pre-test was conducted, which comprised five short-answer questions (ten marks per question; maximum 50 marks). Scenarios pertaining to the same topics were devised for problem-based learning. To enable small-group discussion, the students were randomly assigned to two groups. The post-test questionnaire was identical to that used for the pre-test.Results: A total of 61 students (males=26; 42.62% and females=35; 57.38%) participated. The overall mean pre-test scores increased from 26.44±3.58 (95% CI: 25.55-27.34) to 32.74±4.46 (95% CI: 31.62-33.86). The difference between the overall pre- and post-test scores was highly significant (Z=8.604; p<0.00001). However, the gender differences in pre- and post-test scores were not statistically significant.Conclusions: Since problem-based learning offers a standardized method of teaching wherein the knowledge can be applied, it can be used as an adjunct in educational settings that focus mainly on lecture-based learning.