Inhalation challenge with lysine acetylsalicylate (L-ASA) is often used to diagnose aspirin-induced asthma. The aim of this study was to evaluate the specificity and safety of performing L-ASA inhalation challenge with a dosimeter. Twenty-four subjects entered the study: ten ASA-sensitive asthmatic patients, seven non-ASA-sensitive asthmatic patients, and seven normal control subjects. The investigation was performed on two consecutive days. On day 1 a dosimeter inhalation test with methacholine was performed to establish the provocation dose (PD20). On day 2, patients underwent the L-ASA inhalation test, whereby increasing doses of L-ASA (from 1 to 32 mg cumulative dose) were inhaled using a dosimeter and a dose response curve was constructed. In subjects negative to the top dose, an additional oral dose of 500 mg of aspirin was administered to exclude aspirin sensitivity not revealed with the inhaled drug. The ten ASA-sensitive asthmatic patients developed early reactions within 30 minutes of PD20 administration. Recovery time from induced bronchoconstriction varied from two to three hours to six hours or longer resulting in an "early prolonged reaction." The response was limited to airways. No clear late reactions were observed. There was no correlation between PD20 with methacholine and PD20 with L-ASA. The L-ASA challenge was negative in the seven non-ASA-sensitive asthmatic patients and in the seven normal control subjects. In conclusion the dosimeter method is sensitive, specific, and safe for the detection of aspirin-induced asthma.