Dear Stephane, could you please take a look at metropolis_draw.m It contains a check options_.sub_draws>NumberOfDraws that I think is wrong. NumberOfDraws relates only to the draws within each block (the maximum index allowed for each chain). But sub_draws are the draws across all chains. My hunch is that the check should be something like options_.sub_draws>NumberOfDraws*mh_nblck Best, Johannes -------- Johannes Pfeifer Haußerstr. 29 72076 Tübingen Tel.: +49-(0)7071-6396184 Mobil: +49-(0)170-6936820 jpfeifer@gmx.de