Backgrund: Lobaplatin, D-19466, l,2-diamminomethyl-cyclobutane-platinum-(II)-lactate, is a new watersoluble platin complex which showed a better therapeutic index than cisplatin or carboplatin in murine and human tumor models. Preclinical toxicology studies showed myelosuppression with predominant thrombocytopenia as the dose-limiting toxicity in rodents. Materials and Methods: The phase I study group of the AIO performed the phase I study with Lobaplatin administered as an intravenous bolus injection repeated every 4 weeks without hydration. Results: The maximum tolerated dose was 60 mg/m2, thrombocytopenia was the dose-limiting toxicity. The nadir occurred after 2 weeks with recovery within a week. Mild anemia and leukopenia were found with a nadir after 3 weeks. Nausea and vomiting occurred in half of the patients, however, they were well controlled by antiemetics. No alopecia, renal, CNS or ototoxicity were observed. Overall, Lobaplatin is well tolerated. The intravenous bolus injection without the need for hydration makes this therapy suitable for outpatient therapy. One partial remission was observed in a patient with an adenocarcinoma of the lung. Conclusion: The recommended dose for phase II studies is 50 mg/m2 every 3-4 weeks in good-risk patients with a normal kidney function.