Hi, I've just committed a new version to the repository that uses omega-style (flat array) register allocation instead of etex-style (sparse array). This means that luatex now has 65536 (2^16) of each of the registers \newcount \newskip \newmuskip \newdimen \newtoks \newbox \newmarks The marks code is completely new, and not very optimized yet, but it should not be much worse than pdfetex for a 'normal' document (when no more than 50 or so separate mark classes). Cheers, Taco