Dose-related decreases in food consumption, body weight and weight gain were found in adult male and female Wistar and CD rats during 90 days of feeding of 0, 0.03, 0.125, 0.5, 2.0 or 5% terephthalic acid (TPA) in the diet. Statistically significant decreases in these parameters were confined mainly to the two highest dietary levels of TPA. TPA was more toxic to CD than Wistar rats in that body weights were also significantly lower at the 2% TPA dietary level in both male and female CD rats at 4 and 13 weeks. Five unscheduled deaths occurred between 4 and 13 weeks in animals ingesting 5% dietary levels of TPA. Three of these five deaths involved CD females, which by this and the parameters mentioned above, exhibited the greatest sensitivity to the toxic effects of TPA. No bladder stones were observed in the five dead animals at necropsy. However, trichobezoars (hairballs) were found in the gastrointestinal tract of one CD female. Trichobezoars also were noted in 4 of 7 parental rats (one Wistar male and female and two CD females) that died during the one-generation study. Diarrhea was observed in some of the rats ingesting high concentrations of dietary TPA. A one-generation reproduction study was conducted in tandem with the 90-day feeding study.