It seems my problem is with the rand48 function. With Boost_1_29_0 ---> sizeof(boost::rand48)=8 e.g. the size of a double. With Boost_1_33_1 ---> sizeof(boost::rand48)=16 e.g. twice the size of a double. Because of the truncation that happened with the boost_1_29_0 We were seeing a correctly randomized distribution for the exponential_distribution. Is this a config problem? If so, where do I fix the "boost::rand48" to be a "double" again? I did run the boost ./configure on the Boost_1_33_1 directory before I started using it on the Sun Sparc Solaris8 machine. Thanks, Dave