The successful operation of a plant depends upon an early identification of the problem(s) for remedial action and thus subsequent optimisation of the plant performance. Radiotracer techniques are widely used all over the world to identify the malfunction(s) in process equipment in various industries without shutting down the plant thus leading to high economic benefits. The main objective of this paper is to describe and review the various industrial applications of radiotracer techniques and thus to exploit the potential benefits of these well-developed and established techniques. The emphasis is made on informing the reader about different aspects or radiotracer technology for troubleshooting, process control and optimisation with an exhaustive literature survey. Basic aspects of radiotracer technology such as advantages of radiotracers, criteria of selection of radiotracer for a particular study, amount of tracer to be used, preparation of radiotracer for a particular study, injection and detection of tracer and radiological safety aspects are briefly discussed. The industrial applications of radiotracers are divided into three categories and each application is briefly described with illustrating examples from chemical and petro-chemical process industries. The measurement of residence time distribution and its various applications in industry are discussed in detail. The criteria for estimation of economic benefits grown out of the various applications and current and future trends in radiotracer technology are also discussed.