Lipoprotein(a) [Lp(a)] has been identified as an independent, inherited risk factor for atherosclerotic vascular disease. An elevation of Lp(a) plasma levels has been documented in several series of uremic patients submitted to maintenance dialysis treatment methods or after renal transplantation. We have measured the plasma levels of Lp(a) using an enzyme-linked immunosorbent enzyme method in 19 patients treated with continuous ambulatory peritoneal dialysis (CAPD). Mean (+/- SD) concentration of Lp(a) was significantly higher in the patients than in the 19 healthy controls (51 +/- 48 mg/dL v 16 +/- 15 mg/dL, P < 0.005). No significant differences in Lp(a) levels were found between diabetic patients (n = 5) and nondiabetic patients (n = 14) or between patients who had (n = 6) or had not (n = 13) suffered a previous major cardiovascular complication. No correlation was evident between Lp(a) levels and the patients' ages, period of time on CAPD treatment, or any other lipid-lipoprotein investigated parameter. The mechanisms accounting for the elevation of Lp(a) levels in CAPD patients as well as the specific value of increased Lp(a) concentration as a cardiovascular risk predictor in uremic patients remain thus far speculative. Additional experimental and clinical studies are warranted before the administration of drugs to attempt to lower Lp(a) levels in CAPD patients can be recommended.