Consider the following simple file: % -*-latex-*- % Document name: /tmp/foo.ltx % Creator: Nelson H. F. Beebe [[log in to unmask]] % Creation Date: Wed Oct 15 12:13:15 1997 \documentclass[]{article} \documentclass[]{article} \usepackage[]{amsmath} \newenvironment{fancyequation} {\hrule \begin{equation}} {\end{equation}\hrule} \begin{document} \begin{fancyequation} a = b \end{fancyequation} \end{document} When I run it on my local TeX system, or on the TeXlive one, I get an error: $ /cdrom/texlive/bin/sparc-solaris2.5/latex foo.ltx This is TeX, Version 3.14159 (Web2c 7.0) (foo.ltx LaTeX2e <1996/12/01> patch level 1 Babel <v3.6h> and hyphenation patterns for american, english, french, dutch, ge rman, loaded. (/cdrom/texlive/share/texmf/tex/latex/base/article.cls Document Class: article 1996/10/31 v1.3u Standard LaTeX document class (/cdrom/texlive/share/texmf/tex/latex/base/size10.clo)) (/cdrom/texlive/share/texmf/tex/latex/amslatex/amsmath.sty (/cdrom/texlive/share/texmf/tex/latex/amslatex/amstext.sty (/cdrom/texlive/share/texmf/tex/latex/amslatex/amsgen.sty)) (/cdrom/texlive/share/texmf/tex/latex/amslatex/amsbsy.sty) (/cdrom/texlive/share/texmf/tex/latex/amslatex/amsopn.sty)) (foo.aux) Runaway argument? ! Paragraph ended before \equation was complete. <to be read again> \par l.18 If I comment out the \usepackage command, it works as expected: $ /cdrom/texlive/bin/sparc-solaris2.5/latex foo.ltx This is TeX, Version 3.14159 (Web2c 7.0) (foo.ltx LaTeX2e <1996/12/01> patch level 1 Babel <v3.6h> and hyphenation patterns for american, english, french, dutch, ge rman, loaded. (/cdrom/texlive/share/texmf/tex/latex/base/article.cls Document Class: article 1996/10/31 v1.3u Standard LaTeX document class (/cdrom/texlive/share/texmf/tex/latex/base/size10.clo)) (foo.aux) [1] (foo.aux) ) Output written on foo.dvi (1 page, 312 bytes). Transcript written on foo.log. Is this exposing a bug in the implementation of \end{equation} in the amsmath package? Ordinarily, there should be no problem in using an \end{environment} inside the definition of another macro. ---------------------------------------------------------------------------- - Nelson H. F. Beebe Tel: +1 801 581 5254 - - Center for Scientific Computing FAX: +1 801 581 4148 - - University of Utah Internet e-mail: [log in to unmask] - - Department of Mathematics, 105 JWB [log in to unmask] - - 155 S 1400 E RM 233 [log in to unmask] - - Salt Lake City, UT 84112-0090, USA URL: http://www.math.utah.edu/~beebe - ----------------------------------------------------------------------------