In this paper, we study a cooperative network with one source-destination pair and a relay assisting their communication. All terminals have multiple antennas, which enables them to transmit multiple streams simultaneously. Both the source and the relay use spatial multiplexing to transmit while the receivers at the relay and the destination are linear MMSE receivers. We extend some of the well known digital relaying protocols to multi-stream case and also propose two new adaptive protocols to reduce error propagation at the relay. We evaluate the block error rate of all the protocols and show the benefit of stream by stream decisions at the relay.