We have carried out an in silico exploration of the genomes of Aspergillus nidulans, Aspergillus fumigatus, and Aspergillus oryzae, and identified components of G-protein/cAMP-mediated signaling. Putative G-protein coupled receptors (GPCRs) were distributed over nine classes. The GPCRs within classes were well conserved among aspergilli but varied in other ascomycetes. As previously observed in A. nidulans and other fungi, three Galpha, one Gbeta, and one Ggamma subunits of G proteins were identified in A. fumigatus, whereas an additional likely non-functional Galpha subunit was present in A. oryzae. While most fungal species had five proteins containing the regulator of G-protein signaling (RGS) domain predicted to participate in attenuation of G-protein signaling, A. fumigatus and A. oryzae had an additional RGS protein (RgsD) related to RgsA of A. nidulans. Genes encoding adenylate cyclase, a regulatory subunit and two catalytic subunits of the cAMP-dependent protein kinase, were also identified in the three aspergilli. Finally, regulators of cAMP signaling including low- and high-affinity phosphodiesterases were identified. Taken together, our data indicate a striking diversity at the GPCR level, but little diversity of components at the G-protein and cAMP-signaling level. This may reflect the abilities of these fungi to adapt to various ecological niches and to integrate diverse environmental cues into highly conserved cellular processes.