UBB.threads PHP Forum Software Community Forums Resources and Customizing How Do I? How to check which groups a user belongs to?

I have got several custom user groups which I need to check the access to some custom pages. As far as I have seen, there's no built in function or variable to check which groups a user belongs to.
Is it right that I have to query the USER_GROUPS table directly each time, to check if one user is in a certain group? Or is there another way? Just to be sure.