OBJECTIVE To evaluate the distribution pattern of apolipoprotein(a) [Apo(a)] phenotypes in Koreans and the effect of dialysis modality on serum lipoprotein(a) [Lp(a)] concentration according to apo(a) phenotype in patients with end-stage renal disease (ESRD). METHODS Cross-sectional study. METHODS A university hospital. METHODS 153 normal controls, 99 hemodialysis (HD) patients and 82 continuous ambulatory peritoneal dialysis (CAPD) patients. METHODS Fasting serum Lp(a), lipids, and apo(a) phenotypes were measured. RESULTS The frequencies of the subjects with apo(a) phenotypes of high-molecular weight only, including S3, S4, or S5 or null type were 95.4% of control, 100% of HD patients, and 95.1% of CAPD patients. The frequent apo(a) phenotypes in Koreans consisted of S4, S4S5, S5, and S5S5 isoforms. Significant difference was found in serum Lp(a) concentration among controls and HD and CAPD patients [median (Interquartile range): 0.05 g/L, (0.01-0.19); 0.19 g/L, (0.10-0.35); 0.63 g/L, (0.28-0.90), p < 0.001]. Lp(a) levels in CAPD patients were significantly higher than in HD patients for all four common apo(a) isoforms found in Korean subjects. CAPD patients had higher total and LDL cholesterol levels, and higher ApoB levels than HD patients. Significant differences were found in serum albumin levels between controls and HD and CAPD patients (44 +/- 3 g/L, 40 +/- 4 g/L, 32 +/- 7 g/L, respectively, p < 0.05). There were significant inverse correlations between serum albumin and Lp(a) (r = -0.33, p < 0.01), total cholesterol (r = -0.31, p < 0.01), LDL (r = -0.39, p < 0.01) or ApoB (r = -0.35, p < 0.01) in ESRD patients. A significant positive correlation was found between serum albumin and ApoA1 (r = 0.24, p < 0.01). CONCLUSIONS These findings indicate that Koreans have mainly high molecular weight apo(a) phenotypes and serum Lp(a) is elevated in CAPD patients compared to HD patients for common apo(a) phenotypes, which may contribute to the frequent cardiovascular mortality in CAPD patients.