An experiment involving 35 White Leghorn hens was conducted to study the influence of graded levels of supplemental yellow grease on rate of food passage (transit time). Seven experimental diets (0, 5, 10, 15, 20, 25, and 30% supplemental fat) were formulated. Transit time was determined by utilizing either Cr2O3 or 144Ce as indicators. First appearance of the markers in the excreta and percentages of the markers ingested that were recovered in excreta 10 hr after feeding were criteria used to determine transit time. There was a significant (P less than .01) linear effect of fat on transit time of Cr2O3 whereby the time required for the marker to appear in the excreta increased with increments of supplemental fat. Average first appearance time of Cr2O3 was 193, 219, 214, 227, 251, 250, and 270 min for the diets containing 0, 5, 10, 15, 20, 25, and 30% supplemental fat, respectively. Transit time of 144Ce also was increased slightly (P less than .10) by fat supplementation. Transit time, measured as percentage of marker recovered in excreta 10 hr after feeding, was faster for the control than for the fat-supplemented diets, although the linear effects of fat were not statistically significant (P greater than .10). The results show that supplemental fat increased transit time of ingesta in chickens. This observation may be helpful in understanding the nature of the extrametabolic effect of fat in poultry diets. By increasing transit time, supplemental fats may improve digestibility of other dietary constituents and thereby increase the utilization of dietary energy.