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Design rainfall is a fundamental input to the planning, design and operation of many water and environmental projects. Most countries have derived their own generalised design rainfall data, which is generally expressed in the form of intensity-duration-frequency (IDF) curves. In Qatar, situated in arid region, the existing IDF data was developed in 1991 using a limited data set. This paper presents the development of new IDF data for the State of Qatar using method of L-moments and index regional frequency analysis approach with the mean rainfall as the scaling factor. The daily rainfall data from 32 stations located in Qatar and nearby Gulf countries has been used to form a homogeneous region based on the criteria of Hosking and Wallis. It has been found that the Pearson Type 3 distribution best fits the 24-hour duration annual maximum rainfall data in the Qatar region. For ungauged case, a prediction equation is developed where mean annual maximum rainfall is expressed as a function of physiographic characteristics. From a leave-one-out validation, it has been found the developed prediction equation can estimate mean annual maximum rainfall with a median relative error of 5.5%. Finally, an approximate method is used to obtain design rainfalls for other durations due to the limitations of continuous pluviograph data. The new set of IDF curves are based on a much bigger dataset than the existing 1991 IDF curves. It is expected that the new IDF curves will have wider application in Qatar and will provide a statistically sound basis for storm water design, flood and environmental studies.