We present a position-based neighbour prefetch algorithm for client-server based walkthrough. This algorithm predicts which neighbouring viewcell will be needed in the near future according to the current view position of the client and prefetches the pre-computed potential visible set (PVS) for that viewcell to the client-side cache. Our algorithm has a low memory requirement for the client-side cache. With the same cache size, our algorithm offers a much better performance than the simple neighbour prefetch method. We also provide a delta-transmission algorithm to optimize the prefetch transmission procedure by avoiding transmitting those geometries that are already in the client-side cache. A cache management and entry replacement strategy is also proposed to maintain the client-side cache.