Aims and background To evaluate the response rate, toxicity and survival of patients with AIDS-related Kaposi's sarcoma (AIDS-KS) treated in a phase II clinical trial of pentosan polysulpate (PPS), an inhibitor of basic-fibroblast growth factor (b-FGF) which blocks the growth of Kaposi's sarcoma cells both in culture and in animal models. Patients and methods Between March 1992 and March 1994 16 homosexual males with histopathologically confirmed AIDS-KS were accrued for this phase II clinical trial. PPS was administered at the dose of 25 mg/m² q6 hrs at day 1, followed by 25 mg/m² q12 hrs daily by a subcutaneous injection. The number of patients to be included in the trial was calculated according to the two-stage Gehan method. Toxicity was graded according to the NCI Common Toxicity Criteria, while responses were evaluated according to the WHO Criteria adapted for KS lesions. Patients were all homosexual males, median age 35 (27-43) years, performance status (WHO) 1 (0-2), NYU stage II-IV and prior therapy included vincristine and etoposide (3 cases), local irradiation (4 cases) and meges-trol acetate (2 cases). Concomitant AZT (zidovudine) was given to 3 patients, while DDI (dideoxyinosine) was administered in one case. Results A median of 5 (3-11) weeks of therapy was administered to the patients. Pain at the injection site and low grade fever were the only toxicities observed. Drug-related effects on coagulation parameters or thrombocytopenia were not observed in the trial. One objective response (6%) was documented, which lasted for 9 weeks, while stable disease was observed in three patients, lasting for 11, 9 and 5 weeks, respectively. Conclusion This is the first observation of objective antitumor activity with a b-FGF inhibitor in patients with AIDS-KS. Considering its novelty and the lack of significant toxicity, the authors suggest that this experimental approach deserves further evaluation.