In this paper, we present an efficient event-driven frame capture technique for CMOS image sensors. In the proposed scheme, read-out is not carried out systematically and sequentially for all pixels. Instead it is initiated by each individual if its value has changed since the last frame capture. This approach is shown to lead to an efficient use of the transmission bandwidth, low power operation and improved imaging quality. Results from a 0.35µm CMOS implementation are presented.