As documented in the manual ("Pitfalls"), BOOST_FOREACH is a little awkward to use with associative containers. I've used the following in the past to simplify my own code, and wondered if it was suitable to add to the Boost Foreach library proper. std::map<int, int> my_map; BOOST_FOREACH_PAIR(int key, int value, my_map) std::cout << key << " : " << value << "\n"; The BOOST_FOREACH_PAIR macro is a clone of the BOOST_FOREACH macro with an extra for loop in it to assign both first and second from each pair in the map. If either is not wanted, ignore from Boost.Tuples can be used: std::vector<int> values; BOOST_FOREACH(boost::tuples::ignore, int value, my_map) values.push_back(value); References can be used just as with BOOST_FOREACH, to create a modifying loop: BOOST_FOREACH_PAIR(int key, int& value, my_map) value += key; There are a few alternatives to my solution that I have seen: (1) Predeclare a pair and use it each time around the loop: std::pair<int, int> kv; BOOST_FOREACH(kv, my_map) std::cout << kv.first << " : " << kv.second << "\n"; This adds overhead from copying pairs, and does not give meaningful names to the two halves of the pair. It also has no simple extension to a mutating loop that I am aware of. (2) Typedef the value type of the map before the loop, and use .first and .second: typedef std::pair<const int, int> KeyValue; BOOST_FOREACH(KeyValue const& kv, my_map) std::cout << kv.first << " : " << kv.second << "\n"; This removes the copying overhead, and is easy to change to a mutating loop, but still does not meaningfully name the key and value (3) Use Boost.Tuple's tie to turn the single assignment of BOOST_FOREACH into a double assignment: int key, value; BOOST_FOREACH(boost::tie(key, value), my_map) std::cout << key << " : " << value << "\n" This gives meaningful names, but has copying overhead (albeit not in this simple example). It also has no simple extension to a mutating loop that I am aware of. The key objection to all of these alternatives, from my point of view, is simply that they are unnecessarily complicated. The new macro is much cleaner. Implementation of BOOST_FOREACH_PAIR is simple: turn the innermost assignment loop of BOOST_FOREACH into a pair of loops, one assigning key, one value. Cheers, Chris Purcell