Sixteen rabbits were fed a 1% cholesterol diet with an intraperitoneal injection of saline (n = 8) (cholesterol-diet group), or 50 mg glycosaminoglycans-polysulfate (GAG-PS) (n = 8) (GAG-PS group). After 10 weeks all rabbits were sacrificed and studied. Eight rabbits on a standard diet with an intraperitoneal injection of saline (n = 8) (standard-diet group) were processed in the same manner. After 10-weeks of feeding, the plasma total cholesterol of the GAG-PS group was significantly lower than that of lower than that of the control group (P less than 0.02). The VLDL cholesterol of the GAG-PS group was also significantly lower than that of the cholesterol-diet group. There were no differences in LDL-cholesterol, HDL-cholesterol or plasma triglycerides between the groups. Total lipoprotein lipase activity (T-LPL) (LPL + HTGL) of the GAG-PS group at 10 weeks was higher than that of the cholesterol-diet group. These elevated T-LPL levels were mainly due to an increase in the LPL from peripheral tissues. ADP-induced platelet aggregability of the GAG-PS group significantly decreased at 10 weeks when compared to the cholesterol-diet group, and antithrombin-III activity of the GAG-PS group was inversely increased when compared to the cholesterol-diet group. Although there were no differences in aortic levels of total cholesterol and uronic acid between the GAG-PS group and the cholesterol-diet group, the surface involvement of the aorta in the GAG-PS group was significantly lower than that in the cholesterol-diet group. The aortic levels of free cholesterol, hydroxyproline and calcium of the GAG-PS group were significantly decreased when compared to the cholesterol-diet group. These findings suggest that GAG-PS has antiatherosclerotic effects.