A fundamental problem for signal processing in wireless communications is the separation of multiple signals/users from their mixture. The problem is simpler if they are nonoverlapping in either the time domain or the frequency domain. Two signals may be overlapping in both time and frequency, but they can still be easily separated if they are uncorrelated (orthogonal), as in code-division multiple-access (CDMA) systems. It may be interesting to know that two signals may be overlapping in both the frequency and time domains and not orthogonal to each other, but they can still be separated if each autocorrelation function at the receiver is separable in the time-lag domain. In this paper, we will show how noise-loop (NL) modulation, which was originally thought to produce security at the physical layer, can be used to effectively separate uncoordinated/nonorthogonal users sharing the same time and frequency interval. To show the potential of the NL multiple-access (NLMA) scheme, the theoretical analysis is carried out and compared with simulations. In particular, together with the error probability, a new figure of merit is derived: the multiuser efficiency index. It can be shown that the NLMA scheme is able to distinguish the bit stream of the users, regardless of their number. In addition, the capacity region of the NLMA scheme is derived and compared with the conventional CDMA scheme. All of the aforementioned features, together with the intrinsic security, make the NL an interesting scheme for wireless technology.