AbstractIn a study conducted for the USAF Rome Air Development Center to improve reliability prediction for spacecraft approximately 2600 incident reports on 300 spacecraft (representing 100 programmes) that were launched between the early 1960s and January 1984 were analysed. The causes of the spacecraft failures and the severity of the observed effects are examined.The classification of causes is explained in detail and examples of each type of failure are provided. Differences in the relative frequency of certain causes between pre‐1977 missions and later ones are analysed and some significant trends are identified. The association of spacecraft subsystems with the major causes of failure is investigated. Finally, the severity of the failure effects due to the identified cause categories is discussed. A significant finding is that a large fraction of the incidents is due to design and environmental causes rather than to random failure