Sometimes, the normal maintenance data recorded by repair shops, working around systems as small as cars or as large as factories, can be used to perform reliability evaluations both in terms of distribution of times to first failure and in terms of expected number of failure in a given time interval. Some examples fiom the field show the use of two estimation procedures proposed for parts and systems respectively, in the context of Non-stationary Stochastic Process. Every attempt has been made to make the whole work practice-oriented, as well as in relation to dimensioning and managing the repair shops themselves.