DNAs from three grasshopper species and three locust species (Family Acrididae, Order Orthoptera) have been characterised by a variety of biochemical techniques as part of a general investigation of their molecular evolution. Base compositions were inferred from thermal denaturation profiles and analytical CsCl and Cs2SO4 pcynography. Repeated sequence content of the genomes was studied by renaturation kinetics incorporating absorption measurements. Relative genome size was measured by microdensitometry of nuclear preparations.