In this paper, the CSK/SSMA ALOHA system with nonorthogonal sequences which combines the ALOHA system with Code Shift Keying (CSK) using nonorthogonal sequences is proposed. The throughput performance was evaluated by theoretical analysis. Moreover, the throughput performance of the system is compared with those of the DS/SSMA ALOHA and M-ary/SSMA ALOHA systems. It is found that the throughput performance of our system to be better than those of the other two systems.