This paper presents closed-form expressions for the end-to-end performance of wireless dual-hop systems with multiple amplify-and-forward relays and multiple users over Rayleigh flat fading channels. These results are based on the statistics of the harmonic mean of two random variables related to exponential distribution. Two generalized scheduling policies are considered in the systems for selection diversity from multirelay and multiuser: the centralized scheduling (CS) and the distributed scheduling (DS). Numerical results show that the performance of DS can be degraded when large number of relays are used relative to the number of users. Additionally, it is shown that DS is quite competitive with CS at small number of relays that can be considered to be desirable.