BACKGROUND The role of organic anion transporting polypeptide 5A1 (OATP5A1) a member of a family of drug transporters that mediate cellular uptake of drugs has not been characterized so far. METHODS Gene expression levels of OATP5A1 in small cell lung cancer (SCLC) cell lines were determined by real-time qPCR and chemosensitivity of HEK-293-SLCO5A1-transfected cells to satraplatin in MTT assays. RESULTS Significant expression of this transporter was found at the mRNA level, primarily in drug-resistant SCLC cells, and SLCO5A1-transfected HEK-293 cells showed higher resistance to satraplatin. OATP5A1 is found preferentially in cytoplasmic membranes of tumor cells, including SCLC. CONCLUSIONS OATP5A1 seems to effect intracellular transport of drugs and may participate in chemoresistance of SCLC by sequestration, rather than mediating cellular uptake. Since satraplatin failed to improve survival in SCLC patients, the relation of OATP5A1 expression to clinical drug resistance and its use as marker of chemoresistance should be further investigated.