A 62-year-old Japanese male with an erythropoietin-producing adrenocortical carcinoma is presented. The elevated erythropoietin level and erythrocytosis returned to normal after surgical removal of a huge left adrenal tumor weighing 1,580 g. A histopathological diagnosis of adrenocortical carcinoma was made. Despite adjuvant combined chemotherapy, the patient died of lung and liver metastases 3.5 months after operation. Although the possibility that the elevated plasma erythropoietin level and erythrocytosis resulted from local kidney hypoxia, caused by pressure from the huge adrenal tumor, cannot be completely neglected, the positive cytoplasmatic evidence of immunoreactive erythropoietin in the carcinoma cells and the detection of a high erythropoietin level in the tumor extract on radioimmunoassay confirmed that this is a very rare case of erythropoietin-producing adrenocortical carcinoma.