The effect of delay in gastric emptying rate (GER) caused by oil on the bioavailability of sodium salicylate was investigated. The bioavailability of sodium salicylate administered in aqueous, glycerin and oily vehicles was compared in rabbits. Glycerin (having no effect on GER and more viscous than oil) was used to eliminate the effect of viscosity of the oil on the bioavailability of the drug.. Glycerin formulation was compared with both aqueous and oily formulations using a two-way crossover test in eight rabbits, in each study. The results indicate that the oily formulation gave a lower rate of absorption and a greater extent of absorption than the other formulations. No significant difference in the rate and extent of absorption was shown between the two vehicles having no effect on GER (aqueous and glycerin vehicles). In conclusion, Delaying effect of the oil on the GER enhances significantly the bioavailability of salicylate. This enhancement is due to the physiological effect of the oil on the GER and not due to its viscosity. Possible reasons for the differences are discussed with particular reference to the effects of oil on the gastric emptying rate (GER).