Pegylated interferon and ribavirin combination therapy is the standard treatment for patients with chronic hepatitis C (CHC), but treatment failure can be difficult to predict. We and others have reported a relation between lipid values and sustained viral responses in patients with CHC. However, the relationship between lipid values and treatment failure has not been previously reported. The present study investigated the association between the profiles of phospholipids and free cholesterol (FC), the main constitutive ingredients of the surface of lipoprotein, classified according to particle size and hepatitis C treatment, and determined the usefulness of these parameters for predicting the outcome of treatment. Fifty-five patients with CHC (33 men and 22 women) were included in the study. The serum total cholesterol, triglyceride, phospholipids, and FC levels in the lipoprotein subclasses were determined using high-performance liquid chromatography with gel permeation columns, enabling the lipoproteins to be classified into 13 subclasses according to particle size. According to a univariate analysis, the treatment failure group had a significantly higher serum phospholipid level overall in the high-density lipoprotein (HDL) and medium HDL fractions as well as a higher serum FC level in the HDL fraction and all HDL subclass fractions compared with the corresponding values in the non-nonvirological response group. Higher serum phospholipid and FC concentrations in the HDL subclasses were predictive of a failure to respond in patients with genotype 1b.