This study reports the frequency of new clinical orders, diagnoses, or testing after initial abnormal results of selected serum chemistry tests in 122 hospitalized patients at a Veterans' Administration Hospital. This study also reports the frequency of new orders, diagnoses, or testing after initial abnormal test results in relation to the test's classification as basic, common, less common, or unlisted in the workup and management of patients belonging to 24 common diagnostic related groups as classified by the College of American Pathologists. By chart review, initial abnormalities of serum potassium, creatinine, or blood urea nitrogen were most frequently followed by changes in treatment. For tests categorized as basic, abnormal creatinine and potassium were always followed by changes in treatment. Results were similar for tests categorized as common. Few abnormalities were found in tests categorized as less common.