Lipoprotein(a) [Lp(a)] has recently been characterized as a genetically determined risk factor for atherosclerosis and thrombosis. Normally, Lp(a) serum levels are closely related to the apo(a) phenotype. We studied Lp(a) serum levels and apo(a) phenotypes in 136 young subjects, aged 0.8-24.7 y, including patients with glomerular disease and normal renal function (n = 28), patients with chronic renal failure (n = 20), patients treated by hemodialysis (n = 10), peritoneal dialysis (n = 16), and renal transplantation (n = 23), and in controls (n = 39). Of all, 21 patients had proteinuria in the nephrotic range. The distribution of Lp(a) levels in normal subjects was skewed to the left with 97% having levels below 300 mg/L. A subpopulation with increased Lp(a) levels (13-42%) could be detected in all groups with renal disease, and increased mean serum Lp(a) levels were found in patients with nephrotic range proteinuria, in patients with chronic renal failure, and in patients on peritoneal dialysis. Serum Lp(a) levels were not correlated with age, gender, type of renal disease, renal function or severity of proteinuria, but were correlated with the apo(a) phenotype. For a given phenotype, Lp(a) levels tended to be higher in patients than in controls. We conclude that increased Lp(a) serum levels are frequently found in young patients with chronic renal disease, possibly predisposing them to an increased risk for atherosclerosis and thrombosis.