CAPD related infections and catheter loss continue to be the major problems facing the peritoneal dialysis patient. Few risk factors for infections and catheter loss have been identified. We hypothesized that overweight and underweight patients may be at increased risk for infections and catheter related problems. We examined the effect of the patient's weight at the start of peritoneal dialysis on the subsequent peritonitis and catheter infection rates, as well as catheter loss. Weight was expressed as a percentage of ideal body weight (IBW). Those patients who were more than 110% of IBW were considered to be overweight, 90 to 110% of IBW normal and less than 90%, underweight. An equivalent percentage of patients were overweight and underweight at the initiation of peritoneal dialysis (55/228, 24% for both groups). Overweight, normal, and underweight patients had peritonitis rates of 1.0, 0.9, and 0.8 episodes/y and catheter infection rates of 1.1, 1.2, and 0.8 episodes/y, respectively. Despite these similar rates, catheter loss due to infectious complications was greatest in the overweight group and least in the underweight group (p less than 0.05). No obvious explanation for the difference in catheter loss rate was found. Neither S. aureus nor P. aeruginosa infections occurred more frequently in the overweight patients. However, S. aureus infections more often led to catheter loss in the overweight patients. Catheter loss due to catheter leaks and failure to drain was similar in the three groups of patients. We conclude that deviation from ideal body weight at the initiation of dialysis is not a risk factor for CAPD related infections.(ABSTRACT TRUNCATED AT 250 WORDS)