Fenclozic acid emerged in the late 1960s as a promising carboxylic acid non-steroidal anti-inflammatory drug candidate that demonstrated potent anti-inflammatory, anti-pyretic and analgesic properties. Whole body autoradiography showed fenclozic acid distribution into all tissues except the brain, with radioactivity still detectable in blood, kidney and liver at 72 h post-dose. Fenclozic acid was compared with aspirin in a double-blind, crossover trial in patients with rheumatoid arthritis. It was concluded that fenclozic acid afforded symptomatic relief and was comparable to aspirin. Unfortunately, hepatotoxicity was observed in subsequent trials and the drug was withdrawn from the clinic.