drop down list - When should I use a select box instead of radio buttons?

I know that a select box takes up less space and is good for lots of options. But should there be any deeper influences to my choice than space? Are there any studies that show users preferring one or the other?

There's also the issue of multi-select vs checkboxes in html, which can be discussed here as well, seeing as the answer will probably be the same.

Answer

I use select when the user doesn't need to know all of the alternative choices available. Autosuggest is useful for a long list. Generally, they know what they want and selects save space. Example: Choose a "State" like California or New York. You would never use radio buttons.

I use radio buttons when the alternatives matter. When I want to user to see what they are NOT choosing. Radio buttons allow you to expand the selection and even use longer text.

Rule of thumb: If it's a long list or the alternatives aren't that important, use a select.