To facilitate teaching of inhalation technique to children, we have developed an aerosol inhalation teaching device by modifying the jacket of a canister nebulizer so that inhalation is accompanied by a horn sound and a flashlight is turned on when the canister is actuated. The device was evaluated in 33 children with asthma who had either never used a canister nebulizer (13 patients) or used incorrect technique (20 patients). The inhalation technique was first taught with conventionally, that is, verbal directions and demonstration with a canister nebulizer for 10 minutes. Only 10 (30%) of 33 children learned the technique. The remaining 23 were then taught with the special device. Twenty of 23 learned the technique within 10 minutes, but three others took longer. In a second study, 22 children, 11 of whom were beginners and 11 incorrect users, were instructed with the teaching device from the beginning. Seventeen (77%) learned the technique within 10 minutes; five others took longer. Most children can be taught the aerosol inhalation technique with this easily constructed device.