Most researchers have found increases of lipoprotein (a) [Lp(a)] in uremic patients, as well as in those undergoing hemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD). The mechanisms for this increase remain unclear. We studied 71 patients undergoing CAPD, 48 men and 23 women. According to the time spent on CAPD, the patients were divided into three groups: group 0: 29 patients at the starting off point of dialysis treatment; group I: 22 patients with an average stay of 15.2 months; group II: 20 patients with an average stay of 69.3 months on CAPD. We have only observed significant increases of Lp(a) levels in those patients initiating the dialysis, but no significant differences are found in the other groups undergoing CAPD for longer periods when compared to the control group. We found no significant relation between Lp(a) levels and peritoneal protein loss, and not with absorption of glucose from the dialysate either. We have found a positive and significant correlation between Lp(a) levels and urinary protein loss (r = 0.41; p < 0.001). It is possible that an element associated with proteinuria might have an effect on the metabolism of Lp(a) in CAPD patients.