We investigated the in vitro influence of chylomicron (CM) remnant and very low density lipoprotein (VLDL) remnant on platelet aggregation in healthy persons. The separation of CM and VLDL remnants from serum was performed using an immunoaffinity gel mixture containing anti apo B-100 and anti apo A-1 antibodies coupled to Sepharose 4B. The preincubation with CM and VLDL remnants significantly enhanced the platelet aggregation in whole blood and in platelet rich plasma (PRP) induced by collagen. This effect was observed in whole blood with the addition of VLDL remnant at the concentration of 5 mu g/ml, and in PRP with the addition of CM remnant at the concentration of 1 and 5 mu g/ml, and with the addition of VLDL remnant at the concentration of 5 and 10 mu g/ml. These results may indicate that increase in remnant lipoproteins may be a part of the reasons for atherosclerotic and thrombotic complications.