Abstract This article is an investigation into Kirzner's concept of entrepreneurial alertness — its mechanism and its antecedents. By drawing from decision theory and schema theory, a model is developed to show how changes in the environment are mediated by entrepreneurial alertness and brought to the situated attention of entrepreneurs for evaluation. Entrepreneurial alertness is seen to be the application of unique schemata that allow the entrepreneur to impute meaning to environmental change that would not be imputed by other managers. It is argued that the alertness that allows entrepreneurs to see opportunity where others do not arises from differences in schematic richness, schematic association, and schematic priming. These three antecedents may therefore form a basis on which enhanced entrepreneurial alertness can be developed.