Microsporidia are recognized as a major aetiological agent in chronic diarrhoea of immunocompromised patients. Their detection by light microscopy is hampered by the small size of the spores. A simple and rapid DNA extraction method has been developed for the detection of microsporidian DNA by PCR directly from stool specimens. It can be performed at room temperature in a 1.5-ml microcentrifuge tube format in less than 1 hour. The subsequent nested polymerase chain reaction permits the detection of 3-100 spores in a 0.1-g stool sample. The amplification products can be verified and the species Enterocytozoon bieneusi, Encephalitozoon cuniculi and Encephalitozoon (Septata) intestinalis distinguished by a simple restriction endonuclease digest.