This paper describes an asthma screening procedure developed to identify children with asthma for an intervention study. Students were classified into three categories based on questionnaire responses (previous asthma, suspected asthma, and no evidence of asthma). Those classified as suspected asthma by questionnaire underwent further testing, including spirometry and exercise challenge. Using the questionnaire alone, the measured asthma prevalence was 32%; the addition of spirometry and step testing reduced this estimate to 9.89%. The diagnosis of asthma was confirmed in 96% of children who saw the study physician. This screening procedure can identify school children with suspected undiagnosed asthma.