The purpose of this study was to develop a model that would establish an optimum length of stay (LOS) for selected diagnoses at Ireland Army Hospital. Utilizing an established computerized data system (IPDS), sixteen single, specific diagnoses were chosen for study, based on frequency of occurrence. The data was broken down into specific age groupings, type of beneficiary, and included only bed days occupied. The study compared three Army hospitals of similar size, population served, services provided, and mission. The findings were that the techniques used in this study provided a means by which the physicians could evaluate the individual patient LOS against the average LOS and range for the average LOS during medical audit. The study resulted in the following conclusions: (1) military personnel have a longer LOS for diagnosis related to heart disease and fractures than dependents or retired personnel; (2) utilization of the Inpatient Data System would facilitate data collection and analysis; (3) administrative policy of placing patients on “quarters” has an effect on the average LOS; (4) age and sample sizes were factors in determining the average LOS; and (5) the average LOS and ranges for average LOS could be determined for dependents or retired personnel and compared to those in the civilian community. The most important recommendations were: (1) ranges for the average LOS should be utilized as a benchmark for the establishment of LOS criteria: (2) physicians should consider establishing separate LOS criteria for active military personnel, dependents, and retired personnel; (3) physicians should consider adding administrative delays as an additional element to be considered when reviewing LOS for active military personnel; (4) patients on quarters should be excluded from data utilized to determine LOS in future studies; (5) ranges should be established for the average LOS, based on the averages obtained from the separate categories of patients; and (6) Army hospitals should request historical data from the Inpatient Data System to establish LOS for specific diagnoses.