Medicare covers two types of physical exams:

one when you’re new to Medicare and one each year after that.
“Welcome to Medicare” physical exam—
A one‑time review of your health, education and counseling about preventive services, and referrals for other care if needed. Medicare will cover this exam if you get it within the first 12 months you have Part B.

Starting January 1, 2011, you pay nothing for the exam if the doctor accepts assignment. When you make your appointment, let your doctor’s office know that you would like to schedule your “Welcome to Medicare” physical exam. Keep in mind, you don’t need to get the “Welcome to Medicare” physical exam before getting a yearly “Wellness” exam.
 
Yearly “Wellness” exam—
If you’ve had Part B for longer than 12 months, starting January 1, 2011, you can get a yearly wellness visit to develop or update a personalized prevention plan based on your current health and risk factors. You pay nothing for this exam if the doctor accepts assignment. This exam is covered once every 12 months.

Note: Your first yearly "Wellness" exam can't take place within 12 months of your "Welcome to Medicare"  physical exam.

~ZT and edited pg 39 Medicare and You 2011