Angioedema is a rare but potentially life-threatening adverse effect of angiotensin-converting enzyme inhibitors (ACEI) which usually occurs within the first weeks of therapy. We report three patients in whom ACEI-induced angioedema began with a late onset of 12-33 months, and who had an irregular, unpredictable course under ACEI therapy. In two patients, other drugs or trauma appeared to trigger some of the episodes. After withdrawal of the ACEI, the trigger drugs were well tolerated in provocation tests and upon re-exposure. To avoid putting some patients unnecessarily at risk for long periods, one should consider this irregular pattern of ACEI-induced angioedema and regularly monitor patients for this adverse effect.