A LaTeX package that facilitates the kind of theorem setup typically needed in American Mathematical Society publications. The package consists of the theorem setup of the AMS document classes (amsart, amsbook, etc) encapsulated in LaTeX package form so that it can be used with other document classes.

Amsthm is part of the (required) AMS-LaTeX distribution, so should be present in any LaTeX distribution.

The ntheorem package offers an alternative approach to similar functionality.

The author is The American Mathematical Society. The package is Copyright © 1995, 1999, 2004 American Mathematical Society.