Proteins and proteases present in midgut tissues of sugar-fed Anopheles albimanus (Wiedemann) males and females were studied by 2-dimensional electrophoresis and zymograms using gelatin and hemoglobin as substrates. Protein patterns differed between sexes. Some proteins were similar in both sexes, but differed in intensity. Sex specific proteins and midgut proteases also were detected. These findings indicate the possibility of sex dependent regulation of midgut proteins and protease production.