The influence of patients' age on survival, level of therapy and length of stay was analyzed from data collected in 792 consecutive admissions to eight intensive care units. Mortality rate increased progressively with age; over 65 years of age, it was more than double that of patients under 45 years (36.8% versus 14.8%). However, mortality rate in patients over 75 years was equal to that observed in the 55 to 59 years group. There was a significant relationship between age and acute physiology score (APS) and the influence of age upon outcome decreased when APS increased. The number of TISS (therapeutic intervention scoring system) points delivered to patients increased slightly but significantly with age (r = 0.14). Standard care was responsible for the main part of this increase. Both in survivors and in non-survivors the length of stay was not different comparing the stay of the oldest patient with that of the younger age groups. We conclude that, in ICU patients, age is an important factor of prognosis but not as important as the severity of illness, and that there is no major difference in outcome of patients over 65 years of age compared to the entire study group of ICU patients.