Increasing competition in the market, due to the application of modern manufacturing technology, deregulation of economies, and privatization or corporatization of government owned enterprises, makes decision makers use of management accounting systems more important (Bromwich, 1990). There have been calls for research into the use of management accounting systems under the changing circumstances (Kaplan, 1983; Shank and Govindarajan, 1989; Bromwich, 1990; Bromwich and Bhimani, 1994). This paper reports the results of a study which offers an explanation for the relationship between intensity of market competition and business unit performance, by incorporating into the model managers use of the information provided by the management accounting system (MAS). To assess the relationship, data were collected from 61 business unit managers by way of personal interviews. The results indicate that the intensity of market competition is a determinant of the use of the information which, in turn, is a determinant of business unit performance. In other words, managers use of the information plays a mediating role in the relationship between the intensity of market competition and business unit (BU) performance. An interpretation of the results is that those organizations which use the information can effectively face competition in the market and thereby improve performance.