Abstract-This article introduces and tests the use of the softoutput Viterbi algorithm in decoding pairs of messages encoded with convolutional encoders and sent through a two-user binary adder channel in the presence of additive white Gaussian noise. Curves relating bit error rate versus signal to noise ratio are presented for each user, for assessing the performance of distinct convolutional codes when each constituent encoder employs either a two-stage or a three-stage shift-register.