Halogenated acetic acids are major disinfection by-products of water chlorination and ozonation. Limited data in experimental animals indicate that repeated doses of dichloroacetic acid (DCA) or single doses of dibromoacetic acid (DBAA) cause testicular damage. In the present study, spermatotoxic effects were investigated in rats given oral doses of 0, 10, 30, 90, or 270 mg DBAA/kg/day for 14 days. In rats dosed with 270 mg/kg/day, there were marked effects on epididymal sperm motility and morphology including the flagellar fusion of 2 or more sperm. Testis weight, epididymis weight, and testicular sperm head counts were mildly reduced relative to control, whereas epididymal sperm counts were substantially decreased. Histologic changes in the testis included retention of Step 19 spermatids in Stages IX to XII, abnormal development of late spermatids, and the formation of atypical structures resembling residual bodies that were observed predominantly in Stages X to XIV and I of the cycle of the seminiferous epithelium. At the dosage of 90 mg/kg/day, effects on spermiation, spermatid development, epididymal sperm counts, sperm motility, and sperm morphology were less severe than at the higher dosage. Reduced caput sperm counts and mild effects on spermiation also occurred at 30 and 10 mg/kg/day. These studies indicate that subchronic exposure to DBAA has the potential to affect reproductive outcome in the rat. Compared to previous studies of DCA (12), DBAA, on a molar basis, appears to be a stronger testicular toxicant than the dichloro analogue.