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Stream flow in arid and semi-arid regions is usually in a form of flash floods that occur in dry bed ephemeral streams. In this research, the three-parameter Muskingum method has been investigated as a tool for flash flood routing in arid zones using data from Yiba catchment in the Kingdom of Saudi Arabia. The method is general; it takes into account both lateral inflows from side tributaries and also lateral outflow which can represent transmission losses. Applying the methodology for ephemeral streams requires some modifications of the assumptions. The ephemeral stream is considered as a long linear channel with a total movement time of the hydrograph that consists of two parts, the translation time and the redistribution time. The translation time is the travel time of the flood between two stations, while the redistribution time is the lag time that is estimated from the conventional Muskingum method due to the reshaping of the hydrograph. Eight runoff events have been studied for the model parameter estimation phase, while another four events are considered for the verification phase. A spreadsheet model has been developed to implement the methodology and checked with data from the published literature. The method shows very good results; the average RMSE value is 3 m(3)/s for the hydrographs of the reconstructed events. The correlation coefficients between observed and calculated parameters show relatively high correlation, i.e., 0.99 for the peak discharges, 0.95 for the time lags, and 0.99 for coefficient of transmission losses (the a-parameter). The maximum transmission loss is estimated to be 84 % of the inflow hydrograph form the studied events. A Monte Carlo approach is followed for the verification of the model. It has been found out that the following set of combination of the routing parameter, i.e., a lower limit of d(1), an upper limit of d(2) and a lower limit of d(3) produces satisfactorily good results for the four independent events. Results indicate that the three-parameter Muskingum method exhibits good results in simulating flash flood routing in arid environments.