The purpose of this investigation was to study the effects of continuous Intralipid infusions on serum HDL and LDL levels in the rat. Male Fischer 344 rats were infused continuously via central venous catheter with 10% Intralipid for 96 h and 5, or 2.5% Intralipid for 14 days. Blood samples were collected during the infusion period for total serum cholesterol, HDL-, and LDL-cholesterol measurements. Food intake was monitored during the studies. Total cholesterol, HDL-cholesterol and LDL-cholesterol levels were significantly elevated following 96 h of infusion with 10% Intralipid with food intake significantly decreased compared to a control group. In a second experiment, animals received a continuous infusion of either 5% Intralipid, 2.5% Intralipid or 0.45% saline for 14 days. Total cholesterol, HDL-cholesterol and LDL-cholesterol were significantly elevated following 14 days of infusion with 5% Intralipid group compared to controls but food intake remained constant for 12 days with no evident toxicity.