Researchers often restrict their sample selection to either December or non-December Compustat companies. However, no one has rigorously investigated the implications of this restriction. This paper compares financial characteristics of December and non-December year-end companies. December year-end firms are larger and have smaller betas as compared to companies with non-December year-ends. There are some strong industry concentrations in December year-ends, most notably in the regulated or recently deregulated industries. Retail sales firms have primarily non-December year-ends. A comparison of leverage ratios does not reveal a stable systematic difference between December and non-December year-end companies.