The volume of data contained in a data warehouse represents a potential resource to provide the basis for detailed and specific reference intervals. Routine chemistry panel testing data were derived from an outreach laboratory patient population of 438,180 people and then screened by multiple data filters to identify a large and demographically diverse reference population. Reference intervals were determined for 4 common analytes: aspartate aminotransferase, alanine aminotransferase, total bilirubin, and alkaline phosphatase. Each derived reference population contained more than 60,000 people with sex- and age-specific subgroups comprising between 495 and 4,949 persons. These intervals are particularly representative of the aging patient population and demonstrate a degree of age and sex diversity not reflected commonly in routine laboratory reference intervals. Warehouse data also can yield other interpretative data, such as percentile ranking of results or disease-specific reference intervals. As the warehouse accumulates data from other disciplines (such as from clinical notes or pharmacy), there is increasing potential for the laboratory to enhance the clinician's ability to diagnose and treat disease.