Translation products were used to monitor changes in gene expression between different strains and developmental stages of Aedes aegypti. Total RNA was isolated from fourth stadium larvae, male and female pupae, and male and female adults collected at fixed time intervals following pupation and ecdysis. Differences in RNA populations were assessed by in vitro translation followed by one- and two-dimensional polyacrylamide gel electrophoresis and fluorography. Variations in gene expression between sexes and during development were examined in Liverpool (LVP) and Rockefeller (RKF) Ae. aegypti strains. Sex-related differences consisted primarily of differing lengths of expression for certain polypeptides, although two-dimensional electrophoresis revealed changes in intensity of a 44-kD polypeptide with a pI of 7.9 between males and females. Fourth stadium larvae, pupae, and adults expressed different translation products, which probably correlated with developmental differences. Strain-related differences were observed between LVP and RKF.