The phototoxic potential of tenoxicam, a new non-steroidal anti-inflammatory drug (NSAID), was investigated following oral and intradermal administration of the drug. No hypersensitivity responses to ultraviolet radiation (UVR) were observed for either orally or intradermally administered tenoxicam. In a parallel in vitro study, human polymorphonuclear leucocytes (PMNL) and mononuclear leucocytes (MNL) were exposed to UVR in the presence and absence of the NSAIDs tenoxicam, piroxicam and benoxaprofen (10-40 micrograms/ml). The generation of reactive oxidants by control and UVR-treated human PMNL and MNL in the presence and absence of the NSAIDs was measured according to the extent of luminol-enhanced chemiluminescence. Only benoxaprofen activated reactive oxidant generation by PMNL and MNL. The results of these in vitro and in vivo studies show that phototoxicity is unlikely to complicate chemotherapy with tenoxicam.