This comes from the ConTeXt manual (section 4, page 65) \starttext \setuplinespacing[height=1mm] \stoptext It gives an error: ! Undefined control sequence. l.2 \setuplinespacing [height=1mm] ? Two pages earlier there is \starttext \setupinterlinespace[height=2] \stoptext And this works, but I am not sure what the number values for height and depth mean. I guess fractions of the normalbaselineskip, but I could not find it defined in the text there. What doesn't work is for example: \starttext \setupinterlinespace[height=1ex] \stoptext But sounds fairly natural to me. However, the error is: ! Missing number, treated as zero. <to be read again> p \!!plus ->p lus \setnormalbaselines ...gridsnapping \else \!!plus \baselinegluefactor \openl... \spacing ...thfactor \points }\setnormalbaselines \setstrut <inserted text> ...nizefont \fi \spacing \plusone \presetnormallineheight \s... \setfontparameters ...tsfalse \the \everybodyfont \synchronizefontstrue ... l.2 \setupinterlinespace[height=1ex] May I kindly suggest that some has a look at this? Hans van der Meer