A cDNA library was constructed from germinating conidia of the obligate biotrophic fungus, Erysiphe graminis DC ex Mérat f.sp. hordei Em. Marchal (Egh). Subtractive hybridization and differential screening were carried out. Two cDNA clones, cEgh7 and cEgh16, which were highly expressed in germinating conidia, but not in ungerminated conidia, were selected for further characterization. The corresponding genomic sequences, gEgh7 and gEgh16, were isolated from a cosmid library and sequenced. The gEgh7 gene contains an open reading frame (ORF) that codes for a 249-amino-acid (aa), Pro-rich polypeptide with a repeated primary structure. Expression studies in planta indicated that gEgh7 may have a function in the development and maturation of conidia. The ORF of gEgh16 is interrupted by two introns of 91 and 119 bp. It encodes a 251-aa polypeptide of unknown function. This gene belongs to a multigene family and is expressed during all developmental stages of Egh in planta and may be associated with hyphal growth.