In Uganda, using survey data, estimates of under-five mortality have only been available at national and regional levels. However, estimation of under-five mortality can be made for districts using small area estimation techniques. The simpler way is to use the Standardized Mortality Ratio (SMR). Literature has shown that use of SMR is subject to unreliable results but no empirical study has verified that this is so. The author used Uganda Demographic and Health Survey data of 1995, 2001 and 2006 in the investigations to explore empirically how reliable is the use of SMR in estimation of relative risk of under-5 mortality. The author applied the coefficient of variation to measure reliability of the SMR estimates. Utilization of the traditional SMR could potentially be associated with very high coefficient of variations. The author recommends that before utilization of SMR, there is need to explore reliability of the results using coefficient of variation.