The vessel sclerosing property of sodium morrhuate is useful in treatment of recurrent joint effusions particularly in cases of knee joint effusions. It also can be employed as an addition to surgical synovectomy. Little is known about the effects of this drug on cartilage. This study was designed to investigate the cytotoxic impact of sodium morrhuate on human chondrocytes and cartilage tissue in vitro. Primary chondrocytes from 13 patients were isolated and cultivated in three-dimensional alginate cultures. Furthermore, femoral cartilage explants of 10 patients were cultivated in vitro. Both chondrocytes and cartilage explants were exposed to mixture of sodium morrhuate and mepivacaine in different concentrations simulating chemical synovectomy. After 48 h, cell proliferation, viability, and cytotoxicity were measured. The cartilage specimens were analyzed for apoptosis by immunohistochemistry. Up to a dilution of 1:600, cells were found to be 100 % viable with a proliferation rate of 74 % compared to controls. From 1:400 onwards, a significant increase in LDH release was measured which reached at dilution of 1:200 74 % of high control, whereas histological examination showed no proof of apoptosis or necrosis in cartilage tissue. The results of this in vitro study demonstrate that the cytotoxic effects of sodium morrhuate on human chondrocytes, which lack their original extracellular matrix, manifest between dilutions of 1:500 and 1:400 and increase with higher concentrations of the drug. This effect was not found for cartilage explants, though.