Had some typos in the previous post, correcting ... --- boost::asio::io_service service1; boost::asio::io_service service2; // dir_monitor callback running in thread 1 void f_handler(const boost::system::error_code &ec, const boost::asio::dir_monitor_event &ev) { TaskObj tsk = new TaskObj(...); // detect event, create task and post functor to thread 2 which handles // tasks service2.post(boost::bind(&TaskObj::do_it, tsk)); } int main(...) { boost::asio::dir_monitor dm(service1); for (/*directory list*/) { dm.add_directory(dir); } dm.async_monitor(f_handler); // setup work to prevent exit and before running io_service shared_ptrboost::asio::io_service::work work(new boost::asio::io_service::work(service2)); // thread to constantly monitor dirs boost::thread t1 = boost::thread(boost::bind(&boost::asio::io_service::run, boost::ref(service1))); t1.detach(); // thread to do tasks as posted by dir_monitor thread and idle if no tasks exists boost::thread t2(boost::bind(&boost::asio::io_service::run, boost::ref(service2))); t2.detach(); while (true) { // do other stuff or idle, don't want main process to exit. }