It needs to be 183 days. Count 100% of days they stayed last year, 40% the year before and 20% the year before and before. For example, if your parent stayed 180 days last year (year 2003) and also 100 days in year 2001, then 180+ 100*0.2>183 days, then they are qualified as resident and you can claim dependent for them. Go look at IRS web site, it says clearly on the definition. Hope this helps.