post display ordering question

I’m trying to cause my posts to display in random order. After help with another post I’ve been able to organize them using:

<?php query_posts($query_string . “&order=ASC”); ?>

this is placed before the loop. It of course, puts the items in ascending order.

What would I type in “&order=_____” to cause them to display in a random order?

Any help would be great!! thank you so much for the support.