This is a tremendously controversial subject that divides people largely on political lines.
Liberals would argue that the police certainly do not treat African Americans the same way that they treat white Americans. They would point to numerous incidents in which police have shot unarmed African Americans (like Amadou Diallo) simply because they felt that they were being threatened. There is also the perception that African Americans are stopped by the police while driving much more than is warranted.
Conservatives, on the other hand, tend to side with the police. They tend to argue that blacks are statistically more likely to commit crimes and that it is therefore logical that police would be more suspicious of them. They argue that the police are doing the best they can in a very difficult job and that they are treating African Americans as fairly as can be expected.