Claim B2 visa visiting parents as dependents?

My parents visited me on B2 visa for about 6 months
in 2001 and about 6 months in 1999.

Can I claim them as dependents in my 2001 return?
Should they be marked as resident or non-resident?
Do they need to file returns here?

Yes!, most of the Tax advisros are ok with it, if the parents ar ein USA , obtained ITIN number and stayed more then 180 days in a single year.