From March 1983 to December 1987 the relation of the occurrence of all episodes of peritonitis in CAPD patients to climatic factors, such as temperature and relative humidity was examined. Altogether 389 episodes were recorded in 239 patients. Peritonitis due to Staphylococcus epidermidis, Gram-negative organisms and culture-negative episodes was most frequent during the hot months of the year, June to October. The occurrence of peritonitis due to Staphylococcus aureus was uniformly distributed throughout the year. Relative humidity did not seem to affect the frequency of peritonitis.