I am not able to use #1#2 arguments... Don't know what is going on. thank you for your help ciro --------------------------------- *Case 1) * \setuphead[chapter][command=\MyChapterCommand] \def\MyChapterCommand{} \starttext \chapter{first chapter} \stoptext *output:* no error message, pdf file produced. Everything as expected. *Case 2)* \setuphead[chapter][command=\MyChapterCommand] \def\MyChapterCommand#1#2{{#1} : {#2}} \starttext \chapter{first chapter} \stoptext *output:* . . . fonts > 'fallback modern rm 12pt' is loaded structure > sectioning > chapter @ level 2 : 0.1 -> first chapter ! Argument of \MyChapterCommand has an extra }. system > tex > error on line 6 in file /home/ciro/Desktop/TGM_SpanishTranslation/test2.tex: Argument of ... 1 \setuphead[chapter][command=\MyChapterCommand] 2 %\def\MyChapterCommand{} 3 \def\MyChapterCommand#1#2{{#1} : {#2} 4 } 5 \starttext 6 >> \chapter{first chapter} 7 \stoptext 8