The objective of this study was to evaluate the role of rhinitis (R) and atopic eczema (E) on asthma severity among asthmatic (A) schoolchildren identified by the International Study of Asthma and Allergies in Childhood written questionnaire (WQ). WQ was applied to parents of 6–7-yr-old schoolchildren (SC, n = 3033), and to adolescents (AD, 13–14 yr old, n = 3487), living in São Paulo, Brazil. An affirmative response to ‘has your child/have you had wheezing/whistling in the last year’ identified those with A, and an affirmative response to ‘the last 12 months has your child/have you had sneezing/runny/blocked nose when he/she you did not have a cold/flu?’ identified those with R. Subjects with an affirmative response to ‘has your child/have you had this itchy rash at any time in the past 12 months?’ were identified as having E. Subjects who had R associated with A were identified as AR and those with A associated with R and E as ARE. A who had at least two affirmative responses to questions for asthma severity: speech disturbance, more than four acute attacks, sleep disturbance, and wheezing with exercise were defined as having severe asthma. 22.1% AD and 24.3% SC were identified as A; 47.1% of those AD and 42.0% SC had AR and 10.0% of those AD and 12.8% of SC had ARE. Considering ARE, AR and A groups, speech disturbance during an acute episode of asthma was significantly higher among ARE AD (20.0% vs. 11.5% vs. 8.7%, p < 0.05), and ARE SC (22.1% vs. 13.9% vs. 10.5%, p < 0.05) in comparison with A. Likewise, more than four acute attacks in the last year was significantly higher among ARE AD (24.0% vs. 14.0% vs. 10.5%, p < 0.05) and ARE SC (32.6% vs. 19.4% vs. 12.8%, p < 0.05) as the frequency of sleep disturbance due to wheezing, for AD (61.3% vs. 42.0% vs. 38.4%, p < 0.05) and SC (77.9% vs. 67.3% vs. 58.4%, p < 0.001) and for ‘wheezing associated with exercise’ for AD (72.0% vs. 47.5% vs. 39.9%, p < 0.001) and SC (36.8% vs. 31.4% vs. 14.1%, p < 0.001). Prevalence of severe asthma was higher among ARE AD (57.3% vs. 31.9% vs. 27.0%, p < 0.05) and ARE SC (52.6% vs. 36.9% vs. 22.5%). In patients with A, the presence of R or E are risk factors for severe asthma, and both together (R and E) are a higher risk.