A polymerase chain reaction (PCR)-based method is described for the identification and differentiation of mosquito species and populations. The method, described first by Williams et al. (1990), employs single 10 base-long primers of arbitrary DNA sequence and results in the amplification of random segments of DNA known as random amplified polymorphic DNA (RAPD). We wished to determine if RAPD of mosquito DNA could be used for the differentiation of species and populations, identification of unknown specimens, and the reconstruction of phylogeny. RAPD of mosquito DNA results in the amplification of a series of DNA fragments of varying length. Most amplified fragments are unique to an individual; however, our data indicated that in each of the five species of Aedes examined, some fragments are species-specific and are present in all individuals of that species. This enabled us to derive a diagnostic profile for each of the five species. A nearest-neighbor analysis of all the amplified DNA fragments discriminated among species on a multivariate basis. Several individuals of Aedes albopictus (Skuse), included in the analysis as "unknowns," were correctly identified as belonging to Ae. albopictus. UPGMA clustering of presence-absence data enabled the separation of different Aedes species as well as different populations of Ae. albopictus. The entomological applications of RAPD include the construction of diagnostic profiles for species identification and differentiation among conspecific populations.