We examined the relationship between the reason for admission to the Medical Intensive Care Unit (MICU), cost of care, and outcome of illness to patient age for 182 consecutive patients admitted to the MICU of a community hospital. The reasons for admission to the MICU for patients 70 yr and older did not differ greatly from those for patients 50-69 yr. Only 1 of 21 patients admitted with cardiopulmonary arrest occurring outside the MICU survived. If these patients admitted after cardiopulmonary arrest are excluded from analysis, 80, 87, 86, 67, and 79% of patients in the 5th through 9th decades, respectively, survived (p greater than 0.05). Of the 51 discharged patients older than 70 yr, 38 were alive after a mean follow-up of 19 months, 8 had died, and 5 were lost to follow-up. Total hospital costs, total hospitalization duration, duration of MICU care, laboratory, radiology, and respiratory therapy costs did not vary with patient age. Because the outcome of MICU treatment is similar for all age groups, and because cost of this care for younger and older patients is the same, age should not be a factor in determining whether or not a patient receives aggressive care in the MICU.