Low density lipoproteins (LDL) in patients with coronary atherosclerosis have a substantially lower content of sialic acid when compared with the LDL from healthy subjects. Desialylated LDL have smaller sizes and greater electrophoretic mobilities than sialylated ones. Desialylated LDL may be responsible for the accelerated development of foam cells in atherosclerosis. In the present study, we investigated a relationship between the electrophoretic mobility of lipoproteins and the number of significantly obstructed vessels in patients with coronary heart disease (CHD). Our findings indicate that when the number of significantly obstructed vessels is increased, the electrophoretic mobility of lipoproteins is high. We also investigated the possible role of serum sialidase activity on lipoprotein desialylation in patients with coronary heart disease. In patients with single vessel disease (p < 0.01) and double-triple vessel disease (p < 0.001) the mean serum sialidase activity was significantly higher than in the control group.