46 patients (17 myelomas, 11 malignant lymphomas, 8 mammary carcinomas, 7 head and neck carcinomas, 2 gastrointestinal carcinomas and 1 ovarian carcinoma) were treated with Permease prepared of bovine testes by Sanabo. 7500 i.u. were given either intramuscular one hour before cytostatic chemotherapy or intraperitoneally with cytostatic agents. There were 2 cases of local irritation on the site of injection and 1 case of reversible anaphylactoid reaction. Results achieved in patients treated with the same chemotherapy in spite of resistance, but with addition of Permease: myeloma CR 2/9, subjective improvement 7/9; 5 patients expired, median observation time: 13 months; non-Hodgkin-lymphomas CR 2/5, PR 2/5; 2 patients expired, median observation time: 9 months; breast cancer PR 2/4, 2 patients expired, median observation time: 5 months, 1 patient with Morbus Hodgkin CR, expired after 24 months. The other patients who received systemic treatment had either primary chemotherapy with addition of Permease, or chemotherapy was altered because of resistance against the prior therapy before Permease was applied. Intraperitoneal application of Permease together with cytostatic agents, usually not used for local therapy because of high rate of irritation like cis-platin, was well tolerated. Complete regression of ascites was achieved in all cases. In 1 of the 4 patients duration of remission was 7 months. Hypotheses concerning the mechanism of action of hyaluronidase in malignant diseases are discussed. The effectiveness of Permease might be related to resistance phenomenon of tumor cells or to alteration of pharmacokinetics of cytostatic agents.