Cellular networking is providing global information access to users on the move. Handoff algorithms allow the users to move among heterogeneous wireless networks. In this paper, the authors have proposed an efficient Adaptive Channel Allocation Scheme (ACAS) where the number of guard channels is adjusted automatically based on the average handoff blocking rate measured in the past certain period of time. The handoff blocking rate and the new call blocking rates are minimized. It is seen that the proposed scheme is far efficient than the static channel allocation scheme.