From small subunit ribosomal RNA gene sequences, a pair of PCR primers were designed to amplify a portion of this gene from five species of microsporidia. The amplified fragments encompass polymorphic restriction sites for the Hphl enzyme, resulting in different restriction patterns in the different species. We tested this identification method both on cultured microsporidia and on clinical samples. On cultured microsporidia the expected amplification bands were obtained even when DNA preparations from only ten spores were analysed. On clinical samples, identification of microsporidia was obtained from crude DNA preparations. This method allows for a rapid and easy diagnosis of human microsporidioses.