Broadcasting in Mobile Ad Hoc Networks (MANETs) is a fundamental data dissemination mechanism with a number of important applications in, e.g., route discovery, address resolution. However, broadcasting induces what is known as the “broadcast storm problem” which causes severe degradation in network performance due to excessive redundant retransmission, collision, and contention. Broadcasting in MANETs has traditionally been based on flooding, which simply swamps the network with large number of rebroadcast messages in order to reach all network nodes. Although probabilistic flooding has been one of the earliest suggested schemes to broadcasting, there has not been so far any attempt to analyse its performance behaviour in a MANET environment. In an effort to fill this gap, this paper investigates using extensive ns-2 simulations the effects of a number of important system parameters in a typical MANET, including node speed, pause time, traffic load, and node density on the performance of probabilistic flooding. The results reveal that most of these parameters have a critical impact on the reachability and the number of saved rebroadcast messages achieved by probabilistic flooding.