Soft-moist cat foods containing 6-13% propylene glycol (PG) induce Heinz body formation and decreased red blood cell (RBC) lifespan in adult cats in a dose dependent manner. Since kittens eat relatively more food/kg of body weight and must expand their blood volume in addition to replacing senescent RBC, the hematologic dyscrasia associated with consumption of PG-containing diets may be exaggerated. To test this hypothesis 21 kittens were divided into 3 groups of 7 each and fed diets containing, 0,6 or 12% PG for 13 w. A dose-related increase in Heinz bodies occurred in the 6 and 12% PG groups within 2 w and persisted throughout the study. Although only slight changes occurred in hematocrit, hemoglobin and red blood cell (RBC) count, punctate reticulocytes increased significantly in the 6 and 12% PG groups indicating accelerated erythropoiesis. Mean RBC survival was decreased in the 6 and 12% groups by 44% and 63% respectively when compared to the control group. The increase in reticulocyte count and reduction in RBC lifespan was greater than observed in adult cats. The greater effect in kittens may be due to greater PG intake and not to an inate susceptibility of kitten RBC to PG.