Active volcanism represents a serious threat for society and the environment. A continuous, efficient and accurate surveillance of active volcanoes is the proper strategy to manage and reduce risks for both the environment and population. A range of observations is generally required, not only for monitoring purposes but also for improving our understanding of processes underpinning volcanic eruptions. Some parameters and phenomena can be observed from space, taking advantage of earth observation satellites in orbit, offering synoptic coverage, timely and frequent sampling, multispectral capabilities and significant cost savings compared with other observing systems. Sometimes, satellite-based observations are the unique opportunity to get systematic and accurate information about volcanic phenomena that, as in the case of eruptive volcanic clouds, may rapidly disperse from hundreds to thousands of kilometres from the source. In this chapter, an overview of the present uses of satellite remote sensing for active volcano investigation and monitoring is provided, focusing on accepted methods and techniques capable of furnishing useful information on volcanic activity and processes.