Genomic DNA from spores of the endomycorrhizal fungus Gigaspora margarita was amplified with two sets of degenerate primers designed on conserved regions of chitin synthase polypeptides. Three chitin synthase (chs) gene portions were identified: Gimchs1, Gimchs2 and Gimchs3, encoding one class II and two class IV chitin synthases, respectively. Gimchs1 and Gimchs3 transcripts were detected by reverse transcription polymerase chain reaction (RT-PCR) during root colonization, whereas none of three mRNAs was revealed during spore germination. The potential role of the genes expressed is discussed in the light of morphogenetic and signalling events.