This article presents some discussion on the role of design engineers in achieving specified reliable requirements with the aid of appropriate tools. Highly reliable products can be manufactured only through effective quality control, relaibility planning and design reviews right from the initial design stage. To enable the reliability of electronic equipment to be estimated, with the object of enhancing the usefulness of the product, a new database in the form of a handbook, the Handbook of Reliability Data, fourth edition, has been compiled by British Telecom. The purpose of the handbook is to provide a common basis for system/product reliability predictions in civil applications, especially telecommunications. This article also describes how the data for the handbook was collected and analyzed, and discusses the application of two models for predicting reliability.