Inhalation of aerosolized lysine-aspirin (L-ASA) has been described as an alternative diagnostic method in aspirin-sensitive asthma. To further understand the pathogenetic mechanism of aspirin-sensitive asthma, we performed L-ASA (Inyesprin) bronchoprovocation test (BPT) in 51 asthmatic patients (45 non-atopic and six atopic asthma). Twenty-six patients showed significant bronchoconstriction after the inhalation of L-ASA. Bronchoprovocation test produced immediate asthmatic responses in 13 cases as well as dual asthmatic responses in four cases, whose late onset asthmatic response was noted at 4-7 h after L-ASA inhalation. We conclude that L-ASA bronchoprovocation might be a useful method for the diagnosis and investigation of aspirin-sensitive asthma. However, L-ASA inhalation can also induce late onset asthmatic responses.