There are several ways to handle this...one way might be to add one day to the 2nd parm, and use "less than". (obviously, you want to make sure both parms are purely date, with a time of midnight)
SET @EndDate = DATEADD(@EndDate,1)
SELECT * from MyTable WHEREdate >= @StartDate ANDdate < @EndDate
Note, I didn't verify the syntax for DateAdd, I don't have SQL open right now, so if it doesn't work, check the syntax in BOL.