Well, I think that depends. If you applied early decision (ED) than you should be receiving your answer soon. Because you are ED, they pretty much have to tell you before the 2009 year is out if they've accepted you, moved you to regular admission status, or rejected you. It seems as if most people are finding out in November for ED. If you haven't heard by December, then CALL!
If you are regular decision, then your timetable is MUCH longer. They have until next spring to tell you their decision. So unless by next year spring (maybe around April/May) they haven't told you, I would call then. Otherwise you'll just have to wait.
Painful though it may be, the schools are not obligated to give you a decision early if you are regular. Although it may seem they "forgot" about you, they haven't. If you weren't called fairly early, it's possible they are either waiting on things from you (grades, PCAT scores, etc...) or seeing what the other applicants they'll interview (which go on until Spring) are like before deciding to you accept or reject you.
So, I wouldn't call them. Your application is super important to you. But imagine you x 1000 other people who are sitting worried about their application.