CAPD outcomes were compared between a group of 301 diabetic patients (mean age +/- SD, 58.9 +/- 12.7 years, 55.8% males) and a group of 1689 non-diabetic patients (mean age +/- SD 57.8 +/- 14.8 years, 55.9% males) treated in 30 centres participating in the Italian Cooperative Peritoneal Dialysis Study Group from 1980 to 1989, with follow-up observation periods of 444 years (mean +/- SD, 1.48 +/- 1.24) and of 3502 years (mean +/- SD, 2.07 +/- 1.91) respectively. CAPD was the first modality for 87.2% of diabetics and 78.1% of non-diabetics (P < 0.001). The percentage of patients who needed a partner for CAPD was 45.9% in diabetics and 30.2% in non-diabetics (P < 0.001). In diabetics compared with non-diabetics, cardiovascular diseases and cachexia were nearly twice and infections other than peritonitis more than three times as frequent in causing death. In diabetics, survival was significantly worse (P < 0.0001) and the relative risk of death 2.13 times higher (P < 0.001). The technique survival and the relative risk of drop-out were not significantly different in the two groups. Clinical problems were the most important cause of drop-out among diabetics. The probability and relative risk of drop-out due to peritonitis, as well as of the first peritonitis episode, were not significantly different between the two groups and between diabetics using or not using intraperitoneal insulin. Days per patient year of hospitalization, excluding the first, were 18.4 in diabetics and 14.3 in non-diabetics. CAPD-related problems caused hospitalization in a similar way in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)