Micro/picocellular architectures for wireless networks have been proposed to provide higher capacity under limited radio spectrum. With smaller cell size, the frequency of hand-off events will increase. This will in turn increase the overheads for processing hand-off events. To reduce the overheads due to frequent hand-off, a cell-cluster concept has been proposed in [1]. In this paper, we propose a call admission control policy for cluster-based micro/picocellular wireless networks, that employs two levels of admission thresholds: one at the cell level and the other at the cluster level. An analytical method is developed to analyze the performance of the proposed policy. The analytical method is then applied to find the values of the admission thresholds such that the throughput of the network is maximized under the condition that a predetermined bound on the call hand-off dropping probability is guaranteed. Compared with call admission policies that employ a single threshold either at the cell level or at the cluster level under the condition that the policies provide the same predetermined maximum level of call hand-off dropping probability, the proposed call admission policy provides significantly better performance.