We investigate multiuser two-way relaying strategies for interference limited systems where multiple pairs of users exchange information with their partners via an intermediate relay node in a two-phase communication scenario. To take advantage of the bidirectional communication structure, we propose that each pair of users share a common spreading signature instead of using distinct signatures as in a traditional CDMA setting. We design the jointly demodulate-and-XOR forward (JD-XOR-F) relaying scheme and derive the decision rule which enables the relay to generate the XORed symbol upon reception of the superposition of user symbols. When the relay has limited computational capability, amplify-and-forward relaying can be applied instead. We evaluate the BER performance for the proposed relaying schemes and show that they significantly outperform the traditional "one-way" CDMA systems.