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This chapter aims to review the main causes leading to dispersal, with an emphasis on proximate factors. I will consider causality in dispersal as any factor that explains variation among individuals (within or across species) in any component of dispersal. For a discussion on ultimate causes and on different types of causation and its terminology, I refer to Chapter 2. I will focus in particular on the multicausal nature of dispersal and the interactions between causal factors, a topic that has so far received rather limited attention (Bowler and Benton 2005). First I will introduce the concept of dispersal, briefly discuss its ultimate explanations, and give an overview of different possible mechanisms. Then after a general introduction on multicausality, I will review the different types of causal factors that may explain dispersal patterns. I will distinguish between causation at the individual level and at the level of the environment, but also consider interactions between these levels; for example, when individuals differ in their sensitivity to environmental cues. A recurring theme in the review will be the different ways in which causal factors affect the three stages of dispersal (emigration, transfer, and immigration). populations. In this review I focus on natal dispersal which is typically much larger in extent than breeding dispersal, and therefore has the largest impact on both individual fitness and population structure. Note that especially at population level, dispersal is often referred to as ‘migration’, but I will avoid the latter term because in ecological research it also refers to regular movements by animals between different locations (eg seasonal or diurnal migration …