The Extremes Toolkit (extRemes) is designed to facilitate the use of extreme value theory in applications oriented toward weather and climate problems that involve extremes, such as the highest temperature over a fixed time period. This effort is motivated by the continued use of traditional statistical distributions (normal, lognormal, gamma, ...) in situations where extreme value theory is applicable. The goal is to write a GUI prototype to interact with a high-level language capable of advanced statistical applications. Computational speed is secondary to development time. With these guidelines, the language R  was chosen in conjunction with a Tcl/Tk interface. R is a GNU-license product available at www.r-project.org. Tcl/Tk is a popular GUI development platform also freely available for Linux, Unix and the PC (see section 8.0.22 for more details). While the software can be used without the graphical interface, beginning users of R will probably want to start by using the GUI. If its limitations begin to inhibit, it may be worth the investment to learn the R language. The majority of the code was adapted by Alec Stephenson from routines by Stuart Coles. Coles’ book  is a useful text for further study of the statistical modeling of extreme values. This toolkit and tutorial do not currently provide for fitting models for multivariate extremes or spatiotemporal extremes. Such functionality may be added in the future, but no plans currently exist and only univariate methods are provided.