LaTeX.org

Another note. \collect@body was designed to fail when the environment contains multiple \par(agraph)s. Luckily, there's a replacement called \Collect@Body in the environ package:

http://www.ctan.org/tex-archive/macros/ ... b/environ/

I'm a n00b, so I didn't understand what the answer meant. After messing around for a while, I devised the following MWE.

\documentclass{report}
\usepackage{amsmath}

\makeatletter
\newcommand{\mycommand}[1]{aa#1zz}
\newenvironment{myenv}{begin \collect@body\mycommand }{ end}
\makeatother

\begin ...