Little is known about the physiological effects of red palm olein (RPO). The effects of red palm olein and palm olein (POL) compared to sunflower oil (SFO), on lipids, haemostatic factors and fibrin network characteristics in hyperfibrinogenaemic volunteers were investigated. Fifty-nine free-living, hyperfibrinogenaemic volunteers participated in this randomized, controlled, single blind parallel study. After a 4-week run-in, during which subjects received sunflower oil products, they were paired and randomly assigned to one of three intervention groups receiving products containing 25 g/day ( approximately 12% of total energy intake) of either red palm olein, palm olein or sunflower oil for another 4 weeks. Anthropometric measurements, blood samples and dietary intakes were measured before run-in, and before and after intervention. The differences in changes in total serum cholesterol response between palm olein and red palm olein (+0.59 vs. +0.18 mmol/l; p=0.053), and between palm olein and sunflower oil (+0.59 vs. -0.003 mmol/l; p < or =0.01) were significant. The low-density lipoprotein cholesterol (LDLC) response in the palm olein-and sunflower oil-groups also differed significantly (+0.42 vs. -0.11 mmol/l; p < or =0.01). Tissue plasminogen activator antigen (tPA(ag)) decreased significantly in the red palm olein group compared to the palm olein-and sunflower oil-groups. No effects were found in other haemostatic variables. Palm olein and red palm olein had no independent effect on fibrin network characteristics. In conclusion, compared to palm olein, red palm olein had less detrimental effects on the lipid profile and decreased tissue plasminogen activator antigen. Studies in larger groups are advised for confirmation of results, elucidation of mechanisms and effects of nonglyceride constituents of red palm oil (PO).