Gillespie.jl (Frost 2016) is a Julia package for stochastic simulation using Gillespie’s direct method (sometimes called the Doob-Gillespie algorithm) (Doob 1945; Gillespie 1977), an approach widely used in many elds, including systems biology and epidemiology. It borrows the basic interface (although none of the code) from the R library GillespieSSA by Mario Pineda-Krch (Pineda-Krch 2008), although Gillespie.jl only implements the standard exact method at present, whereas GillespieSSA also includes other methods, such as tau-leaping, etc.. Gillespie.jl is intended to o er performance on par with hand-coded C code, while maintaining a simple but exible interface.