There is growing interest in investigating compounds of exhaled breath condensates (EBC) as potential noninvasive markers of airways disease processes. Some of these markers have the potential to provide information on the early stages of disease. In this paper, we present a method for collecting EBC during both oral and nasal breathing in infants. Fifty-four infants (mean age, 13.3 months; range, 1-30 months) undergoing infant lung-function testing were recruited for this study. Breath condensates were collected during sedated sleep, using a custom-made collection device. Collections were made for 10 min during normal tidal breathing. Nasal measurements were attempted in all children by placing a face-mask over the nose and mouth and keeping the mouth closed. In 14 infants, oral measurements were made by placing a face-mask over the mouth only and occluding the nose. Condensates were collected successfully in all but one child. The collected volume ranged from 50-550 mu l (mean +/- SD, 281.8 +/- 145.8 mu l). The volume of EBC collected was correlated to age, length, weight, and minute ventilation. Significantly more EBC was collected during oral compared to nasal breathing (354.3 vs. 277.5 mu l, P = 0.03). There were no significant changes in heart rate, respiratory rate, or oxygen saturation during collection. The collection of EBC in young children and infants is feasible and safe, and the method used here allows the successful collection of reasonable amounts of exhaled condensate.