In this paper, a new multiuser detector for synchronous code-division multiple-access channels is developed, and the performance is compared with other multiuser detectors. The proposed multiuser detector is based on spatial-temporal filtering and decision-feedback techniques, hence the name spatial-temporal decorrelating decision-feedback (STDF) detector. An optimum STDF detector is expected to have an exponetial complexity as the number of users grow. A suboptimum STDF detector shows a better performance in terms of probabity of error (or SNR) and asymptotic efficiency as compared to the other suboptimum detectors. Simulation results under diverse channel conditions show that STDF is a banwidth efficient technique, which is an essential requirement for modern wireless communcations. Also the results indicate that STDF performance gains are more significant for relatively weak users.