Endogenous small interfering RNAs (endo-siRNAs) are a newly emerged class of small regulatory RNAs. In Drosophila melanogaster, the production of endo-siRNAs depends on the RNase III enzyme Dicer-2 (Dcr-2). Loss of dcr-2 function reduces the resistance of adult flies to various stresses and shortens their life span. The mutants also exhibit alterations in carbohydrate and lipid metabolism. These findings suggest that the endo-siRNA pathway plays a protective role during exposure to stress and aging in D. melanogaster, possibly by regulating metabolic homeostasis. Here, we describe the methods that were used to discover the phenotypes associated with endo-siRNA deficiency by using dcr-2 null mutants.