Testicular atrophy and reduced epididymal sperm count are known to occur after i.p. administration of high doses of hexavalent chromium to rats. The effect of 0.5 mg kg-1 hexavalent chromium injected i.p. 5 d a week for 8 weeks was investigated in male Wistar rats. A significant reduction in epididymal sperm motility was found at the end of the exposure period. The reduction was reversed after an unexposed period of a further 8 weeks. In addition, a decrease in serum testosterone and an increase in FSH were found at the end of the exposure period. The results indicate that a number of mechanisms may be involved in the deleterious effects of chromate on male fecundity.