about alignment

When requiring alignment do I need to purchase brand new tires or performing alignment on used tires is fine. Basically, what I am trying to ask is whether performing alingment on used tires might be troublesome in some way or in the other hand it will prevent tires from more wearing. Thanx

You need the best tires possible on the vehicle. If your tires are worn from a bad alignment, then you will not get a proper result as the tires may lean one way or the other from the uneven wear as the tire rides on the road resulting poor steering.