Hello John & Steven, Thanks for ur help. I was able to resolve the issue. As per the link http://gcc.gnu.org/onlinedocs/cpp/Search-Path.html "All the directories named by -I are searched, in left-to-right order, before the default directories. The only exception is when dir is already searched by default. In this case, the option is ignored and the search order for system directories remains unchanged." Since we have "boost" directory at default path:/usr/include/boost, it used to look /usr/include/boost before -I<install_path>/boost_1_34_0/boost Workaround Done: used -I<install_path>/boost_1_34_0 Now "boost_1_34_0" is not in default path hence looked first Though this workaround works, let me know if this is the right way to go. Thanks & Regards, Chandan ____________________________________________________________________________________ Boardwalk for $500? In 2007? Ha! Play Monopoly Here and Now (it's updated for today's economy) at Yahoo! Games. http://get.games.yahoo.com/proddesc?gamekey=monopolyherenow