BACKGROUND Self-medication is an increasingly frequent phenomenon worldwide; some studies suggest that there is a relationship with socio-economic and cultural factors. OBJECTIVE To determine the prevalence of self-medication and its related factors in a Colombian city. METHODS Cross-sectional descriptive study, in Pereira, Colombia. We selected 414 adults using simple randomization sampling with houses used as the observational unit. The IRIS-AM instrument was used to collect the information required. RESULTS Four hundred and fourteen (414) people were interviewed, 62.6% were females, and mean age was 44 years; 77.5% of the sample had self-medicated at least once in their life and 31.9% during the last month. The most commonly used medications were: analgesics and antipyretics (44.3%), non-steroidal anti-inflammatory drugs and anti-rheumatic medication (36.4%), and anti-histamine medication (8.5%). The most commonly self-medicated symptoms were: headache (55.7%), cold (16.2%) and muscular pain (13.2%). Multivariate analysis revealed an association between self-medication throughout life and storing medications at home, and between a high level of education and having a favorable opinion of self-medication. Storing medications at home and recommending them to others were associated with self-medication during the previous 30 days. CONCLUSIONS Self-medication rates were found to be similar to those reported globally, but there is not an established pattern for this practice. Associations were found between social and demographic variables and self-medication, which require further characterization. Intention to self-medicate has not been well-described in other studies, and may be an important indicator which will contribute to future understanding of this phenomenon.