The aim of the present study was to determine the prevalence of asthma-related symptoms in a group of primary school children, by means of a questionnaire completed by their parents, and their lung function using spirometry and the forced oscillation technique (FOT). Also investigated were diagnostic labeling and medical prescription. We approached 535 children, from two primary schools in Maastricht, the Netherlands. Completed questionnaires were received from 482 children (90%). Valid lung function values were obtained in 470 of these children (98%). The lifetime prevalence of wheeze and attacks of shortness of breath with wheeze was 29% and 19%, respectively. The period prevalence of wheeze was 15%, 13% reported chronic cough, and 10% attacks of shortness of breath with wheeze. The doctor-diagnosed asthma and bronchitis prevalence was 6% and 19%, respectively. Of the children diagnosed as having asthma, 69% used antiasthma medication; none of the children diagnosed as having bronchitis used antiasthma medication. A symptom-based asthma prevalence of 11% was calculated. Statistically significant differences in spirometric and FOT indices were found between the children with and without complaints. In conclusion, among the 482 investigated children a relatively high prevalence of unrecognized or misclassified, and therefore undertreated, asthma-related symptoms was found. These observations were confirmed by the lung function data, in that we found significant differences in spirometric and FOT indices between children with and without complaints.