Interesting findings relating to aspirin-induced asthma recently emerged. In this distinct clinical syndrome, aspirin and most other nonsteroidal anti-inflammatory drugs that inhibit cyclooxygenase precipitate rhinitis and asthma attacks. Aspirin-induced asthma affects 5-10% of adult asthmatics, but remains largely underdiagnosed. The natural history of aspirin-induced asthma has been described, based on an extensive pan-European survey. All over Europe the disease develops according to a pattern in a similar, characteristic way, which might suggest a common underlying principle. Aspirin provocation tests with improved diagnostic accuracy have been developed, although no in-vitro test has been found to be of diagnostic value. At the biochemical level, aspirin-induced asthma is characterized by a chronic overproduction of cysteinyl leukotrienes. The key enzyme, LTC4 synthase, is overexpressed in bronchi and its mRNA is upregulated in peripheral blood eosinophils. The gene coding for LTC4 synthase exists in two common alleles, one of which appears to be associated with a severe, steroid-dependent type of aspirin-induced asthma. Preliminary observations indicate that new, highly specific cyclooxygenase-2 inhibitors may soon become a safe alternative for aspirin-intolerant patients with asthma.