The dissertation uses perceptual positioning techniques in an industrial marketing context for the purpose of market definition, based on proximity (similarity by grouping) and dominance (preference ranking) judgments subsequently processed by Multidimensional Scaling and clustering techniques. Judgments were expressed on stimuli sets that respondents could modify at will and included any brands and concepts involved in applications development for a given computer line. Judgments of MIS/DP managers in Canadian organizations using Digital Equipment Corporation (DEC) VAX and Hewlett-Packard (HP) HP3000 minicomputers resulted in two distinct market definitions which show the respective brands, concepts and respondents in a common joint space. In each case, two respondent populations were used: a demand-side sample chosen at random from the Canadian Information Processing Society's 1986 Computer Census and a supply-side convenience sample of Congos Inc employees. Qualitatively speaking the DEC and HP results are similar: 3-dimensional demand side and 2-dimensional supply-side market definitions, no sub-markets and existing customer segments based on preference. Reliability and validity issues addressed in the research give credibility to the results obtained and encourage further research.