Interferons are the first type of a new generation of substances, called lymphokines, which allow regulatory manipulation of the immune system and thus offer new treatment options. Since recombinant production became possible, interferons have been available in sufficient quantities for clinical trials. Up to now, in urology interferons have been investigated mostly in the treatment of metastatic renal cell carcinoma. The response rate (complete and partial) found in 19 clinical reviews was 16% (139 of 881 patients). Comparable results had previously only been achieved with vinblastine. The in vitro synergistic effect of the two drugs seems to be confirmed by the first clinical trials. Further preliminary results with have been reported interferons in the treatment of superficial bladder cancer, advanced prostatic cancer and condyloma acuminata.