A newly erected genus, Isostomyia, a recently described subgenus, Phenacomyia, of Culex, and 15 species have been added to the mosquito fauna of Guatemala since the last checklist was published by Clark-Gil and Darsie (1983); therefore a revised list is included. One of the additions is Psorophora cyanescens, a new country record for Guatemala. Its presence in Mexico and Central America is reviewed.