In this paper two mathematical models have been developed for evaluating reliability of a component when component strength is encountered by stress. The distribution of component strength is assumed to follow gamma distribution whereas for stress it is regarded to be normal. It is further assumed that strength and stress are independent and the parameters involved are known. In the first model the shape parameter ‘a’ of gamma distribution is an integer whereas in the second model it is not an integer. A particular case of gamma distribution viz., exponential has been derived and discussed. Some numerical examples have been given to illustrate the models.