The Rainfall intensities, the critical storm duration and the frequency (Return Period) are main variables essential for hydrologic design, planning, and management of water resources projects. The relationship between these three variables is called the Intensity-Duration-Frequency (IDF) relationship and graphically expressed as IDF Curve. The first objective of this study is to develop IDF relationships at various rainfall measuring stations by using Gumbel's distribution method, which deals with extreme values of rainfall data. The second objective was to develop maps of the parameters of IDF relationships for different regions of Sultanate of Oman. These two objectives have been reached from precipitation data collected from Ministry of Regional Municipalities and Water Resources (MRMWR) for 51 stations distributed over Sultanate of Oman. The record length of stations under this study varied but all of them covered at least 12 years, excluding the years with missing data. The maximum rainfall depth values were determined for seven different durations (5, 15, 30, 60, 360, 720, 1440 minutes) and for six return periods (2, 5, 10, 25, 50, 100 years). Bernard's model was adopted to develop IDF relationships for all the stations based on the results generated from the measured data. The parameters of the IDF relationships were calculated by regression. Finally, the contour maps for all the parameters were drawn for determining the IDF relationships for ungauged locations.