p-Ethyltoluene (622-96-8) was for developmental effects in a pilot study using groups of 5 female Charles River rats administered the test substance at dose levels of 0, 100, 300, 750, 1500 and 3000 mg/kg/day on days 6 through 19 of gestation. Surviving animals were sacrificed on day 20 of gestation. Mortalities include 5/5 at 3000 mg/kg/day, 4/5 at 1500 mg/kg/day, and 1/5 at 750 mg/kg/day. The causes of these deaths were still undetermined following necropsy. Inflammation and reddening of the gastrointestinal mucosa and erosions of the stomach lining were found upon postmortem examination of rats at 1500 and 3000 mg/kg/day. Maternal body weight gain was severely decreased at 300, 750, and 1500 mg/kg/day and moderately decreased at 100 mg/kg/day during treatment. Rats at 300, 750, and 1500 mg/kg/day showed an increase in the number of early resorptions and increased mean postimplantation loss when compared with controls. No statistical evaluation was reported in this pilot study.