The hypothesis was tested that wall-to-wall carpets on school classroom floors have a negative effect on the respiratory health of asthmatic children. Asthmatic patients (n = 98) were selected from the records of the Sophia Children's Hospital in Rotterdam. The patients were between 5 and 11 years old. All children had peak-flow measurements three times a day for a 1-month period. The parents of the children completed a diary in which respiratory symptoms and medication use were recorded daily for the same period. Dust samples were taken from classroom floors, living-room and bedroom floors, and mattresses of the children. The dust samples were analyzed for Der p I content, the major allergen of the house-dust mite Dermatophagoides pteronyssinus. The results of the study showed that there was no significant difference between children visiting schools with or without carpeted classroom floors in peak-flow variability, acute respiratory symptoms, or medication use. The Der p I content of dust collected from classroom floors was much lower than of dust collected from homes. There was a significant correlation between peak-flow variability and mattress dust Der p I content in asthmatic children sensitized to dust mites, but not between peak-flow variability and classroom floor dust Der p I content. We concluded that carpeted classroom floors do not contribute to asthma symptom severity, possibly because of the low levels of Der p I on them.