Imatinib is a tyrosine kinase inhibitor with activity in gastrointestinal stromal tumor and a variety of other solid and hematological malignancies. Studies in vitro and in a mouse model suggested that the imatinib might also be active in malignant Leydig cell tumor. We report on the-to our knowledge-first treatment experiment with imatinib in a patient with metastatic Leydig cell tumor. Unfortunately, the tumor progressed during treatment.