This study evaluated knowledge and use of generic drugs in a population-based sample of adults from a southern Brazilian city. The outcomes were: the proportion of generics in total medicines used; theoretical and practical knowledge about generics; and strategies used to buy medicines on medical prescriptions. The recall period for drug utilization was 15 days. The proportion of generics in total medicines was 3.9%. While 86.0% knew that generics cost less and 70.0% that the quality is similar to brand name medicines, only 57.0% knew any packaging characteristics that distinguish generics from other medicines. The highest proportion of generic drug utilization was in the antimicrobial pharmacological group. A brand name medicine (with a brand similar to the generic name) was mistakenly classified as a generic through photos by 48.0% of the interviewees. Among subjects who bought medicines in the 15-day period, 18.9% reported buying a generic, but this result should be interpreted with caution, because the population frequently fails to differentiate between generics and other medicines.