Webexperts

$myquery['tax_query'] = array(
	'relation' => 'OR',
	array(
		'taxonomy' => 'category',
		'terms' => array('cat1'),
		'field' => 'slug',
	),
	array(
		'taxonomy' => 'post_tag',
		'terms' => array('tag1'),
		'field' => 'slug',
	),
);
query_posts($myquery);