Asthma incidence and mortality rates have increased in recent years. The present cross-sectional survey aimed to measure asthma prevalence and risk factors in a random sample of 1,968 individuals (20-69 years of age) in Pelotas, Rio Grande do Sul State, Brazil. Overall prevalence of "current asthma symptoms" was 6%, varying according to diagnostic criteria. Associated risk factors in the crude analyses were: female gender, age 60-69 years, non-white skin color, low education, low family income, family history of atopy and asthma, personal history of atopic disease, smoking, low body mass index, and minor psychiatric disorders. In the multivariate analysis the following risk factors remained associated with "current asthma symptoms": mother and father with asthma history, minor psychiatric disorders, age 60-69 years, household income less than 1.01 minimum wage, history of atopic disease, and female gender. The results highlight the variation in asthma prevalence according to diagnostic criteria and confirm the importance of genetic, social, and lifestyle factors.