A prospective study of the effects of low-dose intravenous immunoglobulin on blood lipids and lipoproteins in chronic inflammatory demyelinating polyneuropathy. To assess the effects of a 12-week treatment course of low-dose intravenous immunoglobulin (IVIg) on blood lipid and lipoprotein concentrations in patients with chronic inflammatory demyelinating polyneuropathy (CIDP). Blood lipid and lipoprotein levels were measured at baseline and again at weeks 3, 6, 9 and 12. Twelve patients received 10 g/kg of IVIg over a period of 5 consecutive days, repeated every 3 weeks for a total of 12 doses. All but one patient received corticosteroids during the study, with a mean prednisone equivalent of 14 mg/day. At baseline, the total cholesterol, triglyceride and LDL-cholesterol were elevated (mean [SD], 5.7 [1.0], 2.7 [1.0] and 3.4 [1.0] mmol/l, respectively), whereas HDL-cholesterol levels were lower (mean [SD], 1.1 [0.3]) mmol/l). All lipid fractions showed a significant rise (p<0.05) from baseline at weeks 3, 6, 9 and 12. Triglyceride and LDL-cholesterol showed significant declines (p<0.05) at weeks 6, 9 and 12. HDL-cholesterol increased significantly at weeks 9 and 12. No serious adverse effects were observed. The data suggest that the beneficial effect of IVIg on lipoproteins is long lasting, reaching a plateau at week 12. This has implications for the treatment of lipidaemia in patients with CIDP.