The effects of access to hay and of restricted feeding on the pharmacokinetics of flunixin administered orally to six healthy ponies were compared in a cross-over study. No access to feed for a few hours before and after flunixin administration resulted in rapid absorption with a mean peak plasma concentration of 2.84 +/- 0.28 micrograms/ml attained in an average time of 0.76 +/- 0.18 h, followed by an exponential decline in plasma concentration. A lower peak plasma concentration was obtained when ponies had free access to hay before and after drug dosing. The mean maximum concentration (Cmax) was 1.30 +/- 0.23 micrograms/ml and maximum time (tmax) was prolonged to a mean time of 7.66 +/- 1.74 h. Free access to hay reduced and delayed the peak plasma concentration resulting in two or three separate concentration peaks in some ponies. The mean area under the plasma concentration-time curve was not significantly different for the two feeding regimens.