Drought is an enormous issue that affects almost all regions of the world. It occurs over tropical regions and higher latitude regions, over flat lands and near mountains, as well as over the central regions of continents and near oceans. The prolonged absence of reduced or no precipitation is associated with descending air, with the advection of dry air, and/or the absence of local moisture sources. As part of its overall effort to carry out research on the climate system, the World Climate Research Programme has established a three-component coordinated activity on drought. There components are mapping out the occurrence and forcing of drought, improving its prediction, and interacting with those affected. This presentation is concerned with the first. This component is concerned with developing a catalogue that summarizes our current understanding of the means through which drought is initiated, evolves and ends including combinations of factors. Examples of large scale factors include ENSO and PDO whereas regional factors include land surface and land area feedbacks. Climate change is also a forcing. This component is also documenting droughts as to structural features including nearby and/or internal precipitation events and it is explaining common and unique features. It is working closely with the other two activities of the overall drought activity to ensure maximum progress and application. Everyone is welcome to join this activity.