The handling of the Babyhaler spacer for inhalation therapy in children 0-3 years old with asthma was tested and the perceptions of the investigators with the instruction of this device to the parents was investigated. It was an open, multicenter study of 182 patients with a treatment period of 2 weeks and a 2-week follow-up period. Thirty pediatricians in Dutch local and university hospitals participated. Using a standardized instruction, the purpose and the application of the Babyhaler were explained and demonstrated, and parents were asked to use the Babyhaler on their own child. The quality of the demonstration was scored and, if necessary, additional instruction was given. In the following treatment period of 2 weeks record card was completed; the convenience score of the Babyhaler and the symptom score were recorded. At the following evaluation visit the handling of the Babyhaler by the parents was re-evaluated. Eighty-nine percent of the parents could use the Babyhaler correctly after one instruction. The instructions of the Babyhaler were considered to be easy in 83% of the cases by the parents and the investigators. During the treatment period the handling score (6 = impossible to use, 1 = very easy) improved from 2.4 to 1.7. At the evaluation visit the correct use was similar to the result at the instruction visit (87%). No differences were found in the ease of handling between the three age groups (0-1, 1-2, and 2-3 years). The application of inhalation therapy via the Babyhaler was favored by 92% of the parents as compared to the former treatment method. We demonstrated that the Babyhaler is easy to use by the parents and that the instruction of the device by practitioners is also perceived as easy.