RNA interference (RNAi) is a gene silencing mechanism that can be triggered by introducing double-stranded RNA (dsRNA) into cells expressing the appropriate molecular machinery, which then degrades the corresponding endogenous mRNA. RNAi can be used for determining gene function and creating functional "knockout" organisms. Here we show for the first time that RNAi can be induced in adult fruit flies by injecting dsRNA into the abdomen of anesthetized Drosophila, and that this method can also target genes expressed in the central nervous system (CNS). Two genes were targeted to investigate the effects of dsRNA injection on their mRNA content; lacZ transgene (expressed either in the gut or in the CNS), and GM06434, the Drosophila homologue of the C. elegans gene nrf (nose resistant to fluoxetine). Both the transgene and the endogenous gene were successfully silenced in adult Drosophila by intra-abdominal injection of their respective dsRNA. We propose that our method of RNAi in adult flies can be used to characterize gene functioning in the CNS without the typical interference in development found in most gene mutation studies.