Hello, While trying to match the escaped "(" I am facing problem. Following is the code snippet : std::string stdString = "abc(def)ghi"; std::string bExpression = "c\\(def\\)g"; // Creating the expression boost::regex boostRegEx ( bExpression, boost::regex::extended ); // my match function boost::smatch boostMatch; std::string::const_iterator itr_begin ( stdString.std().begin()); std::string::const_iterator itr_end ( stdString.std().end() ); bool b_match = false; // Match flags used boost::match_flag_type matchFlags = boost::regex_constants::match_default | boost::regex_constants::match_not_dot_newline | boost::regex_constants::match_single_line; // Trying to match b_match = boost::regex_search( itr_begin, itr_end, boostMatch, boostRegEx, matchFlags ); My expected result is: b_match should be "true" boostMatch should contain "c(def)g" Please help me to fix this problem. Regards, Anurag