Male Fischer 344 rats were administered triethylenemelamine orally at dose levels of 0, 0.5 or 1.0 mg TEM/kg/day, five days per week for four weeks. A separate group of males was administered TEM as a single intraperitoneal injection of 0.3 mg/kg. Following treatment, males were mated with two groups of untreated females for a period of one week each. The uterine contents of untreated females were examined for evidence of a dominant lethal effect as manifested in an increase in the average resorption rate. Significant increases in the resorption rate were seen at 0.5 mg/kg/day for the second breeding period, and at 1.0 mg/kg/day for both breeding periods following oral administration. Significant decreases in the number of implantations, and increases in the average pre-implantation loss and resorption rate were observed following intraperitoneal administration. These effects seen in Fischer 344 rats were comparable to results obtained with other strains following a similar treatment regimen.