Over recent years the clinical importance of invasive fungal infections has significantly increased. Mucormycosis refers to a rare, life threatening, opportunistic disease caused by filamentous fungi of the order Mucorales. Most frequently mucormycosis occurs in patients with ketoacidotic diabetes and in neutropenic patients with acute leukaemia. This study of fifteen patients was conducted to evaluate the clinical characteristics of invasive mucormycosis, and goal was also to propose for an early diagnosis and management as survival can only be improved by aggressive surgery and antifungal therapy. In a retrospective analysis of the biopsy and autopsy records of the Department of Pathology at Szent László Hospital between 1992-2003 were evaluated fifteen histologically documented cases of mucormycosis. The underlying diseases were hematological malignancy with neutropenia in ten cases, chronic leukaemia with neutropenia, chronic leukaemia with latent diabetes mellitus and diabetes mellitus one case each. Three cases did not belong to any typical risk group. An in vivo diagnosis was made only in four patients with a rhinocerebral manifestation. Radical necrectomy and long-term antifungal therapy cured two of them. Two patients died of a generalised infection despite therapy. None of the systemic infections could be cured. The diagnosis was made post mortem in eleven patients. Selected clinical forms of mucormycosis are illustrated with short case reports.