Serum concentrations of Apolipoprotein A-I and A-II, (Apo A-1 and Apo A-II) HDL-cholesterol (HDL-C), Total Cholesterol (TC), triglycerides (TG) and lipoprotein electrophoresis were assayed serially in the second half of normal pregnancy (21 women), in pre-eclampsia (26 women) and in both groups one and six weeks after delivery. In the normal group we found increased concentrations of Apo A-I and HDL-C, which remained unaltered during pregnancy. Apo A-II was unchanged. Correlation coefficients for Apo A-II vs HDL-C and Apo A-I vs Apo A-II decreased gradually towards delivery while it remained at an elevated and unaltered level for Apo A-I vs HDL-C. The Apo A-I/HDL-C ratio was unaltered during the whole study while the Apo A-I/A-II ratio was elevated during pregnancy and the Apo A-II/HDL-C ratio was reduced. These results may indicate a gradual change in the surface structure of the HDL particle or its subfractions. In pre-eclampsia Apo A-I and HDL-C concentrations were reduced, TG was increased and Apo A-II and TC were unchanged when compared with the normal pregnancy group. A more pronounced correlation coefficient was recorded for Apo A-I vs HDL-C than for Apo A-II vs HDL-C and Apo A-I vs Apo II. The results indicate that from an atherogenic point of view normal pregnancy seems more beneficial than pre-eclampsia.