A mobile ad hoc network (MANET) is a group of mobile wireless nodes without pre established infrastructure or central management with frequent changing topology. In the last few years, various routing protocols are targeted specially at MANET have been proposed however little data is available about the effect of various parameters on the performance of these protocols. In this paper, we assess the impact of several terrain areas and pause times on the performance of the two prominent reactive routing protocols; i.e. AODV and DSR and present the results of our simulations. It is observed that the hop-by-hop AODV perform much better for medium size terrain areas while DSR is suitable for small terrain areas. For larger terrain areas, the average end-to-end delay encountered by AODV is very low compared to DSR.