This paper presents an algorithm that emulates atomic read/write shared objects in a dynamic network setting. To ensure availability and faulttolerance, the objects are replicated. To ensure atomicity, reads and writes are performed using quorum configurations, each of which consists of a set of members plus sets of read-quorums and write-quorums. The algorithm is reconfigurable: the quorum configurations may change during computation, and such changes do not cause violations of atomicity. Any quorum configuration may be installed at any time. The algorithm tolerates processor stopping failure and message loss. The algorithm performs three major tasks, all concurrently: reading and writing objects, introducing newconfigurations, and “garbage-collecting” obsolete configurations. The algorithm guarantees atomicity for arbitrary patterns of asynchrony and failure. The algorithm satisfies a variety of conditional performance properties, based on timing and failure assumptions. In the "normal case", the latency of read and write operations is at most 8d, where d is the maximum message delay.