For the most part, they are interchangeable, although I can think of a couple of situations where they are not.
If you use the quantifier 'even', then you can only use 'though'. Even though he said that, I said this.
Good Luck
--------------
To get the most from your Tek-Tips experience, please read FAQ181-2886
As a circle of light increases so does the circumference of darkness around it. - Albert Einstein