A prospective study was undertaken to examine the clinical presentation of peritonitis in patients maintained on intermittent peritoneal dialysis and to determine the value of qualitative and quantitative dialysate cultures, gram stain, neutrophil counts, and a semiquantitative leukocyte test strip for case detection. Seven cases of peritonitis developed among 30 patients who underwent 553 dialyses. In most cases, neutrophil counts, cultures, and leukocyte test strip determinations were done within 48 hours prior to the clinical onset of peritonitis and in all instances failed to provide clues for incipient infection. Peritonitis was associated with a dialysate neutrophil count of >500/mm3 and leukocyte test strips were highly sensitive and specific for the detection of this quantity of neutrophils. A total of 16 dialysate cultures was positive in asymptomatic patients who did not have peritonitis. None of these patients subsequently developed peritonitis with the same organism. Dialysate gram stains, cultures, neutrophil counts or leukocyte test strips did not provide an early diagnosis of peritonitis and their use in the absence of symptoms is therefore not recommended.