BACKGROUND Poor inhaler technique in asthmatics is well documented. The objective of this study was to evaluate the influence of reading the instruction leaflet and the consultant's explanations on the use of the new breath-actuated inhaler (Autohaler 3M). METHODS In this study were participating 379 asthmatic children and adolescents, aged from four to 17 years (mean age: 10; 64% boys), recruited by 80 pediatricians. The use of the Autohaler device was considered to be correct if the shaking, lip position, deep inhalation and apnea were all properly performed. RESULTS The Autohaler was used correctly by 42% of the subjects simply after reading the instruction leaflet (phase I), and by 75% of the subjects who, having failed phase I, received the consultant's explanations (phase II). At the end of phases I and II, the device was correctly used by 84% of the subjects. In multivariate analysis, those under the age of nine years and those with no prior use of inhaler systems accounted for a significant amount of the incorrect use of the Autohaler during phase I. In phase II, only the fact of being less than nine years old was significantly related to incorrect use. CONCLUSIONS More than four-fifths of the asthmatic children and adolescents properly used the Autohaler after merely reading the instructions and after receiving additional explanation from the consultant. The marked improvement obtained after medical explanations underlines the essential educative role of the physician when prescribing. Young children require specific training and particularly careful attention.