Atrazine is a widely used herbicide that has been reported to induce the activity of certain detoxification enzymes and to affect insecticide toxicity in organisms experiencing simultaneous exposure to both atrazine and insecticides. In this study, the effects of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) exposure on protein expression in male and female Drosophila melanogaster adults in both microsomal and cytosolic cell fractions was investigated by 2-dimensional gel electrophoresis. Differentially expressed proteins (vs. controls) were identified using matrix assisted laser desorption-time (MALDI-TOF) of flight mass spectrometry (MS). We identified a total of 28 proteins associated with energy production including glycolysis and mitochondrial respiration as differentially expressed and nine proteins associated with detoxification and response to oxidative stress. Most of these proteins were expressed in one sex or the other but not in both. Surprisingly, the only proteins associated with detoxification were identified as glutathione transferases. No cytochrome P450s were identified which have previously been shown to be responsive to atrazine exposure in D. melanogaster and proposed to be associated with insecticide/atrazine interactions. Results of this investigation support the role of atrazine in affecting mitochondrial electron transport and oxidative stress. However, the role of atrazine in pesticide interactions remains uncertain.