Mucormycosis is an uncommon infection caused by fungi of the order Mucorales. During an 8-year period, mucormycosis was diagnosed in 13 patients from three Madrid hospitals. There were 8 males and 5 females, with ages ranging from 21 to 75 years (mean 45 years). There were several underlying diseases, and 4 patients had more than one. Five had diabetes mellitus, 4 chronic renal failure, 2 acute myeloblastic leukemia, 2 were narcotic abusers and were infected by the human immunodeficiency virus (HIV), 1 had non-Hodgkin's lymphoma, 1 was a carrier of a renal allograft and 1 had systemic necrotizing vasculitis. There were different clinical presentations: rhino-orbital in 3, paranasal in 2, cutaneous in 2, pulmonary in 2, primary cerebral in 2, rhinocerebral in 1, and peritoneal in 1. The diagnosis was made during the first week in 6 patients, in the second week in 4, and it was delayed for more than one month in 2. Fresh examination of clinical samples was carried out in 3 patients and hyphae were visualized in all 3. Cultures were taken in 10 patients and they were positive in 7. All isolates were identified as Rhizopus sp. One patient died within 24 hours without being treated, 12 were treated with amphotericin B and 9 received surgical therapy. Six patients (46%) died. The involvement of central nervous system and the absence of surgical therapy were associated with a poor outcome. These results indicate that mucormycosis can develop in several clinical contexts and has a varying clinical presentation. It is a potentially curable infections when early diagnosed and appropriately treated.