During the past several years, researchers in the U.S. and Europe have developed measurement techniques and analysis tools to estimate the inherent safety of a plant or a processing unit. These tools are based on traditional Boolean mathematical methodologies that are limited by the uncertain and subjective nature of the information analyzed. Preliminary results reported here are on the development of an inherent safety index based on fuzzy logic theory that is an extension of the Boolean theory. The basic ideas of fuzzy logic theory and its application are presented by the inherent safety evaluation of a storage tank. The inherent safety index developed by Heikkila is taken as a base and is compared with the results of the proposed prototype index. It shows the benefits of using fuzzy logic. Strengths and limitations of the proposed methodology are also presented.