The first case of one of the most frequent intestinal microsporidians, Encephalitozoon intestinale, is reported from an AIDS patient in the Czech Republic. The patient experienced diarrhoea and was found to have microsporidia spores in stool. Species determination by electron microscopy confirmed the diagnosis of the microsporidian, E. intestinale. The CD4-count at the time of the diagnosis was 73 cells/mm 3 , IRI = 0.21. Only after symptomatic therapy and rehydration the patient stopped the complaining, and although he refused an antimicrosporidial therapy, the CD4-count one month later increased to 200 cells/mm 3 and patient didn't suffered from diarrhoea. Six months after the first finding of microsporidia, the patient was admitted to the hospital care for progressive encephalopathy and developing wasting syndrome again with the intermittent diarrhoea. The patient was treated with albendazole at that time. Nevertheless, after 14 days of albendazole therapy, he still remained positive for E. intestinale spores in the stool (urine specimens remained negative for all the time). The patient died after a two-month hospitalisation and the apparent cause of death was purulent bronchopneumonia, wasting syndrome with microsporidiosis, and HIV encephalopathy. Generalised mycobacteriosis (MAC) was also found from the autopsy material.

        Key words: AIDS, microsporidia, Encephalitozoon intestinale