This paper looks at the impact of high technology employment concentrations on urban sprawl. A methodology for translating spatial employment patterns, into place of residence patterns, is presented. On this basis, the consumption of land at the urban fringe due to both residential and non-residential uses, is estimated. The method is tested empirically using data relating to the two main outer suburban agglomerations of high technology activity in the Chicago metropolitan area. Two counter-factual situations are simulated. The first relates to a spatial counter-factual whereby the high tech concentrations develop in the city of Chicago or within the inner suburbs. The second presents an industry counter-factual that estimates the land consumption impacts arising from the development of an alternative industrial concentration in the same location. The results of the actual and hypothetical cases are compared. They point to a considerable saving in acreage in all alternative scenarios. Some policy implications are highlighted.