The effects of regular exercise and food restriction were studied in the LA/N corpulent rat up to age 9 months. This congenic strain of the Lister and Albany rat is normotensive, corpulent, and hyperlipidemic when homozygous for the corpulent (cp) gene derived from the Koletsky strain. Food restriction of corpulent animals to the intake of matched lean rats caused body weight to be significantly lower, although not as low as that of the lean animals. Plasma total cholesterol in freely eating sedentary corpulent animals was significantly higher (210 mg/100 mL) than in food-restricted rats (165 mg/100 mL), in which plasma cholesterol was considerably elevated compared with lean rats (80 mg/100 mL). Exercise caused a modest but significant increase in both total and high density lipoprotein cholesterol in both corpulent and lean rats. The rise was greater in corpulent rats and, in food-restricted exercising corpulent rats, the cholesterol concentrations were equivalent to those of freely eating corpulent animals. Systolic blood pressure in lean rats fell slowly from 146 mmHg at 8 weeks to 132 mmHg at 36 weeks and was not affected by exercise. Sedentary corpulent rats showed a rapid rise in systolic pressure from 107 mmHg at 7 weeks to 128 mmHg at 11 weeks. This rise was reduced by food restriction and completely prevented by the combination of food restriction and exercise. Thus, in this strain of rats exercise was associated with higher plasma cholesterol concentrations, while food restriction had limited effects.