The effect of triethylene thiophosphoramide (Thio-TEPA), an alkylating agent structurally related to nitrogen mustard, has been described in 39 cases of very advanced ovarian carcinoma. Of the 39 cases treated, 21 had been previously treated and 18 were new cases. In the 39 cases, 42 cycles were evaluable (table 1). 8 cases showed a varying degree of improvement. Marked regression of growth and improvement of symptoms (regression exceeding 50%) was achieved in 7 cases (table 1). Regression of less than 50 % was achieved in 1 case (table 1). The clinical regression is only temporary. A high percentage of cases had side-effects. Of the 42 evaluable, 29 (69%) had one or more side-effects; particularly 28 showed leukopenia, 11 trombocytopenia, 13 anemia and 3 oral or gastrointestinal toxicity (table 2). In conclusion the therapeutic value of Thio-TEPA in ovarian cancer is small. A review of the literature has not shown that other drugs offer longer survival. The control of advanced disease can reasonably be more optimistic when randomized, prospective, clinical trials are performed. A plan for investigation in this direction is in preparation.