Gemcitabine plus treosulfan (GeT) is under investigation in metastatic uveal melanoma. In this phase II trial, cisplatin was added to a GeT regimen to investigate the efficacy and toxicity of two alkylating agents in combination with gemcitabine. Patients received 30 or 40 mg/m of cisplatin, 1000 mg/m of gemcitabine and 3000 mg/m of treosulfan on days 1 and 8. Therapy was repeated on day 29. A maximum of six cycles was administered. Nineteen patients were included in the trial, of whom 17 were evaluable for response. No objective response was observed; seven patients (41%) had stable disease and 10 (59%) progressed. The median progression-free survival of all 19 patients was 3.0 months [95% confidence interval (CI), 1.8-3.1]; the median overall survival was 7.7 months (95% CI, 1.9-13.8). Grade 3 and 4 thrombopenia and leucopenia occurred in eight and nine of the 19 patients, respectively. The addition of cisplatin to the GeT regimen results in excessive haematological toxicity without improvement in efficacy.