A case of actinomyces peritonitis occurring in a young girl undergoing regular dialytic treatment is reported. The peritoneal localization was the only one detectable and occurred in a patient who at the beginning of the dialytic treatment had received peritoneal dialysis on two occasions. During 4 months of treatment the patient underwent surgical drainage of the peritoneal fluid and medical treatment with various antibiotics. Superinfection with Escherichia coli and Candida, and an acute episode of bronchopneumonia, complicated the course of the treatment which was finally successful.