SQL left join and is null problem

[ronlahav]

i have the folowing query
Select *
From PensiaNew right join GemelNew
ON PensiaNew.Col002 = GemelNew.Col002
WHERE ISNULL(PensiaNew.Col001)

and get the folowing error
"The isnull function requires 2 arguments"
what 2 arguments should i insert into the isnull function in order that i wont see the null fields????