I have escaped the '#' character in the usual way, using a backslash, as '\#' in a btex...etex picture as part of a MetaPost figure created within a ConTeXt document, but the escaped character still causes the ConTeXt processing to fail. Here is an example... \pdfminorversion=5 \definepapersize[LG1][width=4.25in,height=6.875in] \definepapersize[LP1][width=4.25in,height=6.875in] \setuppapersize[LG1][LP1] \definelayout[frontmatter] [topspace=0.222222222222in,header=0.555555555556in,height=6.43055555556in,footer=0.694444444444in, backspace=1.05555555556in,width=2.86111111111in,location=middle, leftmargindistance=0.222222222222in,rightmargindistance=0.222222222222in, leftmargin=0.833333333333in,rightmargin=0.111111111111in] \definefont[TitleFont][Serif sa 3.5] \definecolor[TransparentWhite][b=1,t=0,a=1] \def \FrontMatterTitle { \startreusableMPgraphic{frontmattertitle:\overlaywidth:\overlayheight} matter_paper_width := 4.25in; matter_paper_height := 6.875in; front_left_margin := 0.388888888889in; top_margin := 0.347222222222in; draw (0, 0)--(matter_paper_width, matter_paper_height) withpen pencircle scaled 1bp withcolor white; picture titleText; % == HERE IS THE SOURCE OF THE PROBLEM == titleText := btex {\vbox{\hsize 2.72916666667in \baselineskip 38.0pt \setupalign[flushleft,hyphenated,verytolerant] \TitleFont THE BEGINNINGS OF \#BOOM}} etex; labeloffset := 0bp; label.lrt(titleText, (front_left_margin, matter_paper_height - top_margin)); \stopreusableMPgraphic \reuseMPgraphic{frontmattertitle:\overlaywidth:\overlayheight} } \defineoverlay[frontmattertitle][\FrontMatterTitle] \starttext \setuplayout[frontmatter] {\TransparentWhite\title{...}} \setupbackgrounds[page][background={{frontmattertitle}},state=repeat] {\TransparentWhite\midaligned{...}} \stoptext