Forty-two cases of necrotizing fasciitis (NF) surgically confirmed between January 1991 and October 1995 were retrospectively reviewed. This was done in order to describe the underlying diseases, clinical presentations, etiology and outcome of NF and to assess the prognostic value of a simplified severity scoring system. The system scores changes in consciousness status, body temperature, blood pressure and ventilation to determine the likely outcome of NF. Twenty-five men and 17 women with a median age of 51 years (range, 17-87 yr) were included. Diabetes mellitus (57.1%) was the most common underlying disease. The mean duration of symptoms before admission was 8 days (median, 7 d; range, 1-30 d). The extremities (66.7%) were most commonly involved. Initial clinical presentations within 48 hours of admission included skin erythema and swelling at the affected site (97.6%), pyrexia (61.9%), hypotension (33.3%), altered consciousness (28.6%), bullous lesions (26.2%) and crepitus (9.5%). The mean number of isolated pathogens was 1.8 (range, 0-6). Eight patients had mixed aerobic and anaerobic infections. The attributable case fatality rate was 23.8%. Higher severity score (> or = 4 points), hypotension, altered consciousness, respiratory failure requiring ventilator support, elevation of alanine aminotransferase levels > twofold, serum creatinine > 177 mumol/L, thrombocytopenia (< 100 x 10(9)/L), and worsening symptoms and signs within 48 hours of admission were associated with higher fatality rates (p < 0.05).