 This study evaluates the safety and efficacy of a novel tyrosine kinase inhibitor, PTK787ZK222584, in the treatment of GIST gastrointestinal stromal tumor that is resistant to imatinib mesylate Gleevec. The study participants are required to have histologically confirmed GIST with prior imatinib treatment for metastatic GIST. is administered orally 1250 mgday. Six patients will first enter the study. If clinical benefit is obtained in 1 of 6 patients, 9 and 30 additional patients will be entered into the protocol in two stages a maximum of 45 patients will be entered. Patients who benefit from the study treatment will be treated with PTK787ZK222584 until treatment failure. 