Add the file /functions.php into your theme...

[Carlos]

PHP Code:

function add_scripts() {
    echo "<script src='". get_theme_url() . "/js/utility.js'></script>";
}

add_action('theme-header','add_scripts'); 


Yeh...not working. It prints out the url but not in the script tag.

Replace get_theme_url() by get_theme_url(false) to return the value instead of echoing it.