This study aimed to assess the prevalence and severity of asthma and related symptoms and the associations with gender in 13-14-year-old schoolchildren in the city of Nova Iguaçu, Rio de Janeiro State, Brazil. The cross-sectional study used the self-applied International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. The sample included 3,033 students randomly selected from 37 public and private schools. Prevalence of "any history of wheezing" was 26%, as compared to 11.7% within the last 12 months ("current asthma"), and was higher among girls (PR = 1.46; 95%CI: 1.31-1.62 and PR = 1.72; 95%CI: 1.35-2.21). Symptoms associated with severity, like "sleep disorders" and "speech limited by wheezing" were associated with female gender (PR = 2.57; 95%CI: 1.77-3.73 and PR = 2.07; 95%CI: 1.25-3.43). Although asthma prevalence was lower than in other Brazilian cities, it was still high among schoolchildren in Nova Iguaçu, and was more frequent and severe among girls. Further research is needed to explain the observed differences.