Automated patient classification systems (PCS) are widely used throughout the United States. Their intended purpose is to generate information to be used in decision making by and for nurses and nursing services. Expenditures for this type of information technology are significant, yet no previous research had been conducted regarding the actual use of information generated by an automated PCS. Thus, the purpose of this research was to describe if, how, and why information obtained from an automated PCS is used in hospital decision making. A qualitative design was used for this organizational case study. The study was conducted in a university teaching hospital that used the Medicus PCS. Purposive and theoretical sampling led to interviews with 67 informants. Observations and documents were also used as sources of data. A constant comparative method was used for data analysis. An interpretive description of how and why PCS information is used in hospital decision making was an outcome of this research. Seven categories emerged from analysis of the data. Six categories pertain to how patient classification information is used in decision making. These categories include "planned use", "actual use", "actual non-use", "people use it differently", "consistency of use", and "PCS information as one component of decision making". One category "factors influencing use" relates to why PCS information is used, or not used, in decision making. Results from this study support the theory that multiple perspectives of information use in organizational decision making are necessary to reflect this complex process. Although the majority of the findings from this study are consistent with the literature, there are some exceptions. One is of particular interest. The PCS literature suggests that reliability and validity of a PCS influence use of the generated information. Results from this study do not support this assumption. Several recommendations for nurse administrators and PCS vendors resulted from this study. The findings from this research also suggest implications for theory development. Work toward a theoretical framework of information use in organizational decision making may be facilitated by the nine propositions induced from the case study data.