The study was carried out to investigate the changes of total WBC, neutrophil, lymphocyte, monocite, eosinophil in the horses'blood of 3 groups which randomly assigned 3 heads to each group. In group A(daily therapy), each horse was iniected, intramuscularly, 100 mg of prednisolone acetate/day for 3 days, consecutively. In group B(alternate-day therapy), each horse was injected, 100 mg of prednisolone acetate/day 4 times on alternate days, intramuscularly. In control group, each horse was injected, intramuscularly, the equivalent volumes/day of saline solution fur 3 days, consecutively. The results were summarized as fellows: 1. Total WBC counts in group A rapidly increased until day 4th, which the counts reached the $maximum(13.10{\pm}0.13{\times}10^{3}/{\mu}l$)(p<0.05), and decreased into control group range until day loth. In group B rapidly increased until day 1st, and gradually increased until day 71% which the counts reached the maximum ($12f3{\pm} 0.20$)0<0.05), and decreased into control group range until day 16th. 2. Neutrophil counts in group A rapidly increased until day 4HL which the coun% reached the maxi um($10.85{\pm} 0.08$)0<0.05), and decreased into control group range until day loth. In group B rapidly increased until day 1st and slowly increased until day 7th, which the counts reached the maximum$(9.76{\pm}0.22)0<0.05)$, and decreased into control group range until day 16th. 3. Lymphocyte counts in group A and B rapidly decreased until day 4th, which the counts reached the minimum(2.14{\pm}0.12 and 2.09{\pm}0.20$, respectively) (p<0.05), and increased into control group range until day 10th. Group A and B, however, had no significant effects each other on Iymphocyte counts during the study. 4. Monocite and eosinophil counts in group A and B remained in the range of control group during the study. Eosinophil in group A and B slightly decreased on day 4th, significantly%<0.05), but we could not generally be reliable the result because of severe standard deviations. In conclusion, we fecund that group A had more rapidly increase and decrease than group B on hematologic counts of WBC, but group B had longer period than group A on the hematologic effects of WBC, and found not differences between daily therapy and alternate-day therapy.