This paper studies fair scheduling in ad hoc wireless networks. We propose a credit-based mechanism to ensure fairness for best effort flows. Each flow is associated with a credit value, and is scheduled based on the concept of "the less excess in usage value, the higher the transmission priority". The network is logically partitioned into clusters, each with a scheduler, and an unique code. The schedulers first assign time slots to mobiles in the affiliated clusters. The mobile scheduled to send at the next time slot then in turn assign the time slot to a flow. Each scheduler operates independently, and together, they allow flows in the network to share bandwidth in a fair way. We have also performed simulations to validate the proposed mechanism. The results show that the proposed mechanism provides fair share of bandwidth to all flows, and also improves overall system throughput.