Program E-Surge: A Software Application for Fitting Multievent Models. Multievent models (Pradel 2005, 2008) handle state uncertainty, and they therefore cover a range of situations like hidden capture heterogeneity and sex determination from behaviour which cannot be treated in the multistate paradigm. We introduce a new software application called e-surge, built upon the concepts developed in program m-surge (Choquet et al. 2004) to encompass this new class of capture–recapture models. It also improves on m-surge by allowing the decomposition of transitions into several steps. We present the new concepts involved, notably the event and the multistep process, and how they are implemented in e-surge. We then illustrate the use of e-surge with three examples. One example deals with breeding propensity where the breeding state cannot always be ascertained; a further deals with emigration which is considered as a two-step process (Grosbois and Tavecchia 2003) and the last one with a version of a memory model where survival can be handled directly.