A comparative experimental study was carried out in guinea-pigs to assess the effect of pentoxifylline on inner ear perfusion. Five animals were given a single dose of 30 mg pentoxifylline per 10-minute intravenous infusion and the cochlear blood flow measured by means of the hydrogen-clearance technique before and after administration of the drug. A control group of 11 animals received the solvent only. Compared to controls, a significant increase in inner ear blood flow was observed in the pentoxifylline-treated animals. These data may explain positive clinical findings with pentoxifylline in otological disorders associated with impaired cochlear perfusion.