I agree with others – it is asking for name clashes, ambiguities and then the fact is it is less explicit. While I can see the use of using , my personal preference is to limit it. I would also strongly consider what some others pointed out:

If you want to find a function name that might be a fairly common name, but you only want to find it in the std namespace (or the reverse – you want to change all calls that are not in namespace std , namespace X , ...), then how do you propose to do this?

You could write a program to do it, but wouldn't it be better to spend time working on your project itself rather than writing a program to maintain your project?

Personally, I actually don't mind the std:: prefix. I like the look more than not having it. I don't know if that is because it is explicit and says to me "this isn't my code... I am using the standard library" or if it is something else, but I think it looks nicer. This might be odd given that I only recently got into C++ (used and still do C and other languages for much longer and C is my favourite language of all time, right above assembly).

There is one other thing although it is somewhat related to the above and what others point out. While this might be bad practise, I sometimes reserve std::name for the standard library version and name for program-specific implementation. Yes, indeed this could bite you and bite you hard, but it all comes down to that I started this project from scratch, and I'm the only programmer for it. Example: I overload std::string and call it string . I have helpful additions. I did it in part because of my C and Unix (+ Linux) tendency towards lower-case names.

Besides that, you can have namespace aliases. Here is an example of where it is useful that might not have been referred to. I use the C++11 standard and specifically with libstdc++. Well, it doesn't have complete std::regex support. Sure, it compiles, but it throws an exception along the lines of it being an error on the programmer's end. But it is lack of implementation.

So here's how I solved it. Install Boost's regex, and link it in. Then, I do the following so that when libstdc++ has it implemented entirely, I need only remove this block and the code remains the same:

namespace std { using boost::regex; using boost::regex_error; using boost::regex_replace; using boost::regex_search; using boost::regex_match; using boost::smatch; namespace regex_constants = boost::regex_constants; }

I won't argue on whether that is a bad idea or not. I will however argue that it keeps it clean for my project and at the same time makes it specific: True, I have to use Boost, but I'm using it like the libstdc++ will eventually have it. Yes, starting your own project and starting with a standard (...) at the very beginning goes a very long way with helping maintenance, development and everything involved with the project!

Just to clarify something: I don't actually think it is a good idea to use a name of a class/whatever in the STL deliberately and more specifically in place of. The string is the exception (ignore the first, above, or second here, pun if you must) for me as I didn't like the idea of 'String'.

As it is, I am still very biased towards C and biased against C++. Sparing details, much of what I work on fits C more (but it was a good exercise and a good way to make myself a. learn another language and b. try not be less biased against object/classes/etc which is maybe better stated as less closed-minded, less arrogant, and more accepting.). But what is useful is what some already suggested: I do indeed use list (it is fairly generic, is it not ?), and sort (same thing) to name two that would cause a name clash if I were to do using namespace std; , and so to that end I prefer being specific, in control and knowing that if I intend it to be the standard use then I will have to specify it. Put simply: no assuming allowed.