Hallo. I'm running step() on lm() in R version 2.15.1 within RStudio on my xUbuntu Linux computer with 4 core processor. Linux top command states that rsession (R) is using from 100 % to about 330 % of the processor, which (I think) means that R is using more than one core. Is it possible? I thought that R is limited to one core, unless explicitly using multicore or similar package. If it is so, when it happens? Is there some general statement about this feature? (However, the overall processor use detected by top command is about 30% user load and 40% system load overall when rsession uses 330 % of one processor.) Many thanks. Michal