Sorry if this is double-posted, but my webmail has stripped angle brackets and their contents out of my previous email ... Boost 1.40 on CentOS 5.3 64bit: I have #included boost/regex.hpp in a file but get the following compile time error (mangled by webmail): /tmp/ccXM0HkR.o: In function `boost::basic_regex boost::cpp_regex_traits > >::assign(char const*, char const*, unsigned int)': contact.cpp:(.text._ZN5boost11basic_regexIcNS_12regex_traitsIcNS_16cpp_regex_traitsIcEEEEE6assignEPKcS7_j[boost::basic_regex boost::regex_traits > >::assign(char const*, char const*, unsigned int)]+0x27): undefined reference to `boost::basic_regex

...

::do_assign(char const*, char const*, unsigned int)'

collect2: ld returned 1 exit status

The important bit appears to be 'undefined reference to boost__basic_regex' etc This file definitely exists at /usr/include/boost/regex.hpp. Another Boost #include in the same file (boost/date_time/posix_time/posix_time.hpp) produces no error. 'ldconfig -p' lists libboost_regex.so. What am I doing wrong? Thanks Mike