Thank you all. Your solutions seem quite elegant.

Just a note, I was hoping for something I can do inside the server only declaration, just like I can do with the opposite redirection mysite.com --> www.mysite.com:

[code]
server {
server_name www.mysite.com mysite.com;

if ($host !~* www\..*) {
rewrite ^(.*)$ http://www.$host$1 permanent;
}
[/code]

On the other hand, I feel your solution with the two server declaration can even be a bit faster (not to mention easy to understand). Your solution suggests I should rewrite the above code into two server declarations as well.

Thank you very much!
Jiri