Twenty-five semen samples were collected from five mature boars. Whole semen (with the gelatinous material removed) was incubated at 37° C. for 12 hours. Samples were taken at 0, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 10 and 12 hrs. of incubation for the determination of motility, fructose, lactic acid and pH. At the start of incubation averages were as follows∶ fructose, 50.8 mg./100 ml. (1.33 mg. per 109spermatozoa); lactic acid, 15.4 mg./100 ml.; (0.73 mg. per 109spermatozoa); and motility, 75%. Fructose utilization by 109 sperm per ml. per hr. was 0.18 mg. for the first, 0.07 mg. for the second, and 0.18 mg. for the third hour. During the first hour of incubation 0.43 mg. of lactic acid accumulated, followed by 0.29 mg. for the second and 0.16 for the third. Changes in pH were not severe until after the sixth hour of incubation. Motility closely followed the fructose utilization pattern. Significant boar differences and boar x time interaction were shown for each constituent except pH.