Fifteen Standardbred racehorses were utilized in a 3 x 3 Latin square experiment replicated five times to evaluate the effects of dietary cation-anion balance (DCAB) on whole venous blood values for pH, pCO2, HCO3-, lactate, Na+, K+, Cl-, and Ca2+. The horses were matched according to racing ability and history and randomly allotted to the treatment groups (High, Low, and Basal DCAB). Horses were allowed a 21-day adjustment period on the diets between each rotation. On the last day of each feeding period, blood samples were drawn for determination of the previously mentioned parameters before and after a one-mile warm-up and race and at 60 minutes of recovery. Due to health related problems and complications beyond our control, seven of the original fifteen horses were unable to complete the trial and thus were removed from the data set prior to statistical analysis. This study demonstrated that DCAB did not significantly alter acid-base status of the horse. The pH, pCO2 and HCO3- values were not different (p>.05) across treatments. Furthermore, whole blood values for Na+, K+ and Ca2+ did not differ significantly between treatments. Chloride was not significantly different between diets but was found to be consistently higher in horses fed the low DCAB diet versus those fed the high DCAB diet. No change (p>.05) was observed in plasma lactate concentrations across treatments. These data suggest that horses were able to maintain normal acid-base status regardless of the dietary cation-anion balance of the diet.