Step 3 is 16 hour examination divided over two-days. Each day of testing must be completed within eight hours.
The first day of testing includes 336 multiple-choice items divided into 7 blocks, each consisting of 48 items. Examinees must complete each block within sixty minutes.
The second day of testing includes 144 multiple-choice items, divided into 4 blocks of 36 items. Examinees are required to complete each block within forty-five minutes. Approximately 3 hours are allowed for these multiple-choice item blocks. Also on the second day are twelve Clinical Case Simulations, where the examinees are required to 'manage' patients in real-time case simulations. Examinees enter orders for medications and/or investigations into the simulation software, and the condition of the patient changes. Cases are of 10 or 20 minutes.
Approximately forty-five minutes to one hour is available for break time on each of the two days of testing.
Harshly this is only the last step to pass.
http://en.wikipedia.org/wiki/United_States_Medical_Licensing_Examination