The Simio simulation software does not provide distribution fitting capabilities, and it is suggested to use third-party packages such as StatFit (www.geerms.com), @RISK (www.palisade.com), ExpertFit (www.averill-law.com) and Easyfit (www.mathwave.com). This chapter demonstrates the use of the StatFit package. This chapter also covers how to generate nonstationary arrivals in Simio. This chapter covers using Simio to create theoretical and empirical distributions from a data file. The use of the Rate Table and Source object to create nonstationary arrivals is also shown.