Peritonitis is a serious clinical complication in patients with terminal chronic renal failure (CRF) on peritoneal dialysis (PD). The incidence of peritonitis varies from center to center, and during the last decade it occurs approximately in one patient during 24-60 therapeutical months, which is the result of good education of patients, but also of employing the new systems for PD. Fungi as well as Mycobacterium tuberculosis are rare causes of peritonitis in patients on PD therapy. The incidence of peritonitis with these two causes varies: 1-15% and 0.7-3%, respectively. The most frequent causes of fungal peritonitis are yeasts (Candida species 70-100%, with most frequent C. parapsilosis), but rarely filamentous fungi such as: Aspergillus, Paecilomyces, Penicillium, Zygomycetes, etc. Gram stains are helpful for diagnosis, as well as the culture of peritoneal effluent. There are various kinds of treatment protocols: withdrawal of peritoneal catheters and application of antimicotic drugs such as amphotericin B (which has recently been abandoned), oral flucytosine, oral or intraperitoneal fluconazole (imidazol) or itraconazol in the case of resistance. Although clinical signs disappear, most of these patients cannot continue with peritoneal dialysis therapy because of peritoneal adhesions, abscesses, fibrosis or progressive sclerosing peritonitis. Percentage of death is 12-44%. The incidence of tuberculosis is higher in patients with CRF in comparison with the entire population, and tuberculous peritonitis can develop in patients who had infection with Mycobacterium tuberculosis which was not treated adequately. Diagnosis can be made by detecting mycobacterium in peritoneal effluent (cultivation for 6 weeks) and/or acidophilic bacillus or typical granuloma in peritoneal biopsy. Therapy consists of removing the peritoneal catheter and long lasting antituberculotic therapy: izoniazid, rifampicin, pyrazinamide, pyridoxin (6-12 months). Streptomycin and ethambutol are to be avoided because of side effects in these patients. In spite of therapy, possible consequences are: ultrafiltration loss, obstruction of intestines because of adhesions, abdominal abscesses, fistulae, ending PD therapy, and even death.