We studied the clinical, microbiologic, and histopathologic findings from 14 patients with necrotizing fasciitis; also tissue obtained at autopsy was available from six patients. In all cases, material cultured was positive for multiple organisms, including Clostridia and fungi; organisms were identified by histochemical staining of tissue sections in 12 of 14 cases. The histologic pattern comprised edema, necrosis, and inflammation of skin, subcutaneous fat, and fascial tissue. Hyalin necrosis of sweat glands was observed in five patients. Thrombosis of vessels at all levels was a prominent feature, suggesting that study of coagulation factors may be important. Diagnosis may be confirmed by the histologic picture; however, microbiologic material is essential to guide therapy.