Prompted by reports of tumor regression among patients with metastatic renal cell carcinoma treated by injection of an aggregated autologous or allogeneic tumor antigen with a nonspecific adjuvant, we studied the efficacy of this therapy in 23 patients. Following nephrectomy or excision of a metastatic lesion 16 patients were treated with an aggregated autologous tumor antigen combined with Candida albicans antigen. There were only 2 minimal responses. Seven patients judged unsuitable for an operation were treated with an aggregated allogeneic antigen. There were no objective responses. We conclude that these treatment regimens have minimal activity against metastatic renal cell carcinoma.