The clinical and pathologic features of 49 patients with adrenal cortical carcinoma are presented. The series included 26 men and 23 women with a mean age of 34 years. The average duration of symptoms prior to diagnosis was 6.6 months. Eighteen patients (37%) presented with recognizable endocrine syndromes secondary to excess tumor steroid production. Surgical excision was the only mode of therapy to offer any opportunity for prolonged survival. Nine of the 21 patients (43%) with a completely resectable tumor were alive with no evidence of disease an average of 7.2 years postoperatively. Death due to metastatic tumor occurred in 36 of the 49 patients (73%) an average of 8.7 months following diagnosis. Chemotherapy had no apparent effect on outcome while radiotherapy produced an objective palliative response in 50% of treated patients. The average size and weight of the tumors were 12.4 cm and 875.6 g, respectively. The difficulty of precise pathologic classification of certain large adrenal tumors is discussed and the importance of histopathologic features relative to gross morphologic findings is emphasized.