The conidiogenesis of Geotrichum candidum grown on Czapek agar containing 1% yeast extract was examined by electron microscopy. The results showed that the entire wall of the fertile hypha is incorporated into the conidial wall and also that increase in thickeness of the inner wall layer and differentiation of crosswalls are likely to be due to new wall synthesis which occur during conidium formation. Furthermore, the chemical composition was analysed for the purified conidial walls, and was compared with that of haloarthric conidial walls produced by Trichophyton mentagrophytes.