Geminiviruses have recently emerged not only as the cause of devastating diseases of important crop plants but also as a tool to study fundamental aspects of RNA interference (RNAi) and virus-induced gene silencing. RNA silencing is an evolutionary conserved mechanism protecting cell from pathogenic RNA and DNA, which is increasingly viewed as an adaptive immune system of plants against viruses. Here we summarize recent developments in the field of geminivirology presented by several leading groups at the Meeting "Gemini2004" (a total of 85 participants from all over the world) with the main focus on the anti-viral strategies that exploit RNAi and related silencing phenomena.