Four thousand subjects from Cartagena, Colombia were surveyed in order to establish the prevalence of asthma in this city. They were considered to have asthma when they had consulted their physicians for shortness of breath accompanied with wheezing during the last year and had received asthma medications. Point and cumulative prevalence were 8.8% and 12.2%, respectively. Seventy percent of the affected population was less than 15 years old. There were no significant differences in the prevalence of asthma between sexes. Forty-five percent of asthmatic subjects had family histories of asthma. The prevalence of rhinitis was 16.4% and 30.6% of the patients with asthma. The asthma prevalence of this study is high, indicating that this respiratory disease is a significant health problem in this tropical city.