Crickets of the genus Laupala represent one of the many morphologically cryptic groups of insects, with the most closely related species distinguished only by the male calling song. Cryptic groups provide a challenge in determining the genetic boundaries between closely related populations and species. We have addressed the question of species boundaries in the Hawaiian cricket, Laupala, using nuclear DNA patterns sampled by the amplified fragment length polymorphism (AFLP) technique. This method has been used widely by plant researchers to facilitate the rapid assessment of genetic diversity in very closely related species and varieties. The AFLP technique is simple and robust, can be applied to any organism, and overcomes problems associated with cost, development time, information content and reproducibility that can plague other marker systems. Our results support previously hypothesized taxonomic relationships among sympatric populations and suggest close genetic relationships among allopatric, conspecific populations.