Granulocyte macrophage colony stimulating factor (GM-CSF) is one of the main cytokines involved in tissue damage during rheumatoid arthritis (RA). To investigate the expression of the GM-CSF receptor (GM-CSF-R) in the synovial tissue of osteoarthritic (OA) and RA patients, biopsy specimens were obtained ex vivo during therapeutic arthroscopy. A semi-quantitative polymerase chain reaction (PCR) technique was performed using specific primers for the alpha chain of the GM-CSF-R and for beta-actin. The PCR products were analyzed after slot-blotting and hybridization with specific cDNA probes. Both RA (n = 11) and OA (n = 7) samples were positive. No significant overexpression correlating with the clinical or histological disease status of the patients was observed. In conclusion, GM-CSF-R could be detected in the synovial tissue where it can mediate the effects of this cytokine locally produced during RA inflammation.