Cactus pear (Opuntia ficus indica) is native to Tunisia and the fruit is consumed exclusively as fresh fruit. The seed oil is rich in polyunsaturated fatty acids but the nutritive value of the oil is unknown. The objective of our research was to determine the fatty acid content of cactus pear seed oil and to evaluate the effect of an oil supplemented diet on rats. The main fatty acids of prickly pear seed oil were C16:0, C18:0, C18: 1, C18:2 with an exceptional level of linoleic acid, up to 700 g kg(-1), and a total content of unsaturated fatty acids of 884.8 g kg(-1). Feed intake and body weight of rats were measured every two days during the nine weeks of treatment. Digestibility, feed conversion efficiency and protein efficiency ratio were determined. No difference in digestibility was noted for the oil enriched diet. The results indicated a significant decrease in serum glucose concentration (22%) over the control group. However, an increase in the concentration of glycogen was noted in liver and muscle. Blood cholesterol and low density lipoprotein (LDL)-cholesterol decreased in the treated group. High density lipoprotein (HDL)-cholesterol concentration remained unaltered during the treatment. These findings support the nutritional value of cactus pear as a natural source of edible oil containing essential fatty acids and reinforce the possibility of cactus pear as a new crop for Tunisia especially in semi-arid regions, where conventional crops are difficult to establish. (c) 2005 Elsevier Ltd. All rights reserved.