Semen samples from 19 bulls were added to solutions of NaCl having chloride concentrations of 10, 15, 17, 18, 19 and 20 g/1, and were examined continuously for motility until motility had ceased or 5 hr had elapsed. At chloride concentrations of 10 and 15 g/1 some motility was always present after 5 hr. At 19 and 20 g/1 sperm motility stopped abruptly. At 17 g/1 mean survival time was 2·55 hr. In four bulls which had chloride concentrations in semen of over 2·80 mg/ml, sperm survival time was significantly lower than the average for the other semen samples which had chloride contents between 1 -40 and 2·25 mg/ml. A larger study would be needed, however, to establish whether survival of bull sperm is related to the chloride content of the semen at the time of ejaculation.