Hi, I've decided to use boost::thread to run a background thread in my MPI application. Only one rank has a timer, and I only make some calls to elapsed(). Here is what I get if I print the values I retrieve from this single rank: 2.98 (...) 6.58 6.6 6.6 6.61 6.71 6.73 6.75 2.69 2.69 6.78 2.77 2.77 2.83 6.91 2.87 2.87 6.94 6.96 6.97 2.91 2.91 2.91 2.94 7.02 2.99 3.01 3.01 3.02 3.05 3.05 (...) You may notice that the values are not incresing, which leads to very bad total time in my case. Is there a known interaction between these two classes? I'm trying to create a simple example, but I can't get boost::timer to count sleep() time :| Matthieu Brucher -- Information System Engineer, Ph.D. Blog: http://matt.eifelle.com LinkedIn: http://www.linkedin.com/in/matthieubrucher