1. Dopamine (DA) at low doses (2.5 micrograms kg-1 min-1) produces a measurable increase in glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) in young healthy subjects and has a therapeutic effect in younger patients with congestive cardiac failure (CCF). In elderly healthy subjects, DA increases ERPF but does not increase GFR in all subjects. 2. To determine the potential therapeutic use of DA in elderly subjects with CCF, we studied 17 patients (5 male) aged 79.9 years (range 68 to 93 years) admitted to hospital for inpatient treatment of CCF resistant to diuretic and angiotensin converting enzyme inhibitor therapy. The effects of a single infusion DA at 2.5 micrograms kg-1 min-1 on GFR and ERPF were assessed in a double-blind, placebo controlled prospective study. 3. There were no significant differences in GFR or ERPF between control and DA. A reduction in GFR was seen in some patients. 4. DA at low dosage was not shown to benefit elderly patients with resistant CCF, and in some patients was detrimental. Higher doses or a combination with other inotropes may be necessary for a renal effect in elderly patients.