A procedure for high resolution electrophoresis of isozymes of the mosquito Aedes aegypti using nonlinear (2.5%-20%) polyacrylamide gradient gel slabs is described. Crude mosquito homogenates were electrophoresed on gradient and on homogeneous (7%) polyacrylamide gels and stained for esterase (EST), isocitrate dehydrogenase (IDH) and malate dehydrogenase (MDH). The resulting zymograms were compared to demonstrate the high resolving power of the polyacrylamide gradient gel system.