How Can I unclog my bath tub?

Try plunging it and see if that makes an improvement.
Then try pouring undiluted strong bleach into the drain and leave overnight. Pour down some water to wash it through and then plunge again.
If that doesn't work try a caustic soda (sodium hydroxide) based drain cleaner. Warning: check the instructions on the product to make sure it is suitable before using it. Make sure you wash away the caustic soda before using the bath.

ddd
December 2004