After analyzing a total of 53,097 racing records for 2,928 horses from Korea Racing Horse Association, the results obtained were as follows. 1. Sex-age effect was subdivided into 72 groups, and horse effect was regarded as random(σ²e/σ²h = 1.94). 2. Fifty, four to 56 month-old groups took the largest portion of the total records. Racing performance for geldings, stallions, and mares reached their peaks at 4.5, 4.3, and 3.5 years old, respectively. Comparing with the foreign peak years of 5-6 for racing hones, those in domestic horses were much younger. Due to poor management and frequent races, racing lives of horses were shortened and might result in economic losses. 3. Because geldings are included in the classification of male by KRHA, it is likely that the racing performance for geldings might be underestimated, while stallions may overestimated. 4. Variances for both additive and multiplicative adjustments were the same at 2.68. Correlations between means and standard deviations for racing time by age groups were -0.06, and this low correlation led to the suggestion that additive adjustment factors for racing time were much easier and more desirable.