The work reported in this paper is an attempt to build upon existing research in the DSS area in order to enable the accurate measurement of the degree and extent of DSS usage in organisations. We put forward a framework for the classification of DSS usage which uses two dimensions, the novelty and specifiability of decision situations. This framework can be used by IS researchers to classify DSS applications meaningfully and make comparisons not only across large samples of systems, but also across organisations. In order to prove the validity of our novel approach, we studied and classified 24 Irish organisations based on the extent to which they used DSS for different decision situations using two specific measurements: DSS spread and DSS complexity. The results obtained confirm our initial empirical results (obtained with a smaller sample of organisations). The framework we have developed is a useful vehicle for categorising the extent to which organisations have managed to integrate their DSS staff and DSS applications in the decision making processes of managers at all levels.