The effect of benzbromarone on gluconeogenesis from several gluconeogenic substrates in isolated rat liver cells is reported. Benzbromarone inhibited glucose synthesis from all substrates employed when the drug was used at concentrations half to ten times greater than its therapeutic plasma levels. This inhibition was more pronounced from lactate and pyruvate than from fructose and glycerol. The results are compared with those obtained for probenecid, a classical uricosuric drug. We found that probenecid inhibited the pathway in the same way as benzbromarone.