The paper proposes the use of an adaptive window flow control technique to control data access, with the aim of improving voice performance in an integrated voice/data multiplexer. By means of both mathematical analysis and computer simulation, the proposed control technique is shown to yield improvements in the average packet delay of both voice and data at the expense of data throughput. Additionally, the proposed control technique can be made to perform better than the two frame management strategies which have been demonstrated by previous work to be efficient for the integration of voice and data packets.