Exposure of male Charles River CD1 rats to a 5 percent saccharin diet in utero and throughout weaning, conditions associated with tumor induction, did not induce detectable metabolism (< 0.4 percent of the oral dose) of tritiated saccharin in vivo. No metabolites (< 0.06 microgram per kilogram per 24 hours) were detected in the urine of normal rats given a tracer dose. Pretreatment with 3-methylcholanthrene did not induce saccharin metabolism.