The relationship between user involvement and information system (IS) success factors is not yet well understood despite the number of research projects conducted in this area. IS researchers generally believe that increases in user involvement lead to better systems. IS research to date, however, has yielded conflicting results. IS researchers have typically defined user involvement as a single variable and used user satisfaction as the only measure of system success. Those measures may be inadequate because different types of systems and different degrees of user involvement may affect system success in different ways. This research used Sullivan's Technology Planning Environment model to determine system characteristics and software reliability to supplement end user satisfaction as an additional measure of system success. The research addressed weaknesses in prior research, developed a Systems Environment model of user involvement, and tested the model in a field study. The systems Environment model categorises systems into Traditional, Backbone, Federation, and Complex environments. This research focused on the Traditional environment of the model Systems in the Traditional environment have relatively low impact on the organisation's core business and have a centralised technology structure. Results showed a significant positive relationship between user involvement and end user satisfaction. When involvement policy is included as a covariate, there is also a significant positive relationship between user involvement and software reliability.