The human erythroleukemia cell line K562 was established 1971 from the pleural effusion of a patient with chronic myeloid leukemia in blast crisis. These hematopoietic cells are distinguished by an anchorage independent growth as suspension with a short population doubling time. In this study we characterized the K562 cells regarding to the leptin receptor in order to get an useful tool investigating the properties of this receptor. The cell line K562 expresses the leptin receptor in an especially high level (showed by RT-PCR, Northern blot and Wester blot), as well the long splice form with a signal tranducting function as the short receptor with potential transport and clearance function. Cross linking experiments revealed a specific band with an apparent molecular weight that could be predicted for the glycosylated receptor. Studies with radioactive labeled leptin demonstrated a leptin binding with high affinity in a saturable and reversible fashion. Further more, binding studies revealed that the cells are capable to produce a soluble receptor, probably by enzymatic shedding.