Abstract Does ambulatory blood pressure correlate with the renal function damage better than clinic blood pressure in isolated systolic hypertension, as has been reported in other target organ involvement in combined systolic/diastolic hypertension? We investigated the correlation of serum beta-2 microglobulin concentration and both 24-h urine beta-2 microglobulin concentration and excretion as measures (suggestive) of glomerular filtration rate and tubular reabsorption, respectively with both ambulatory and clinic blood pressure in 19 health normotensive (68 ± 4.9 years) and 50 isolated systolic hypertensive elderly individuals (69 ± 5.4 years). Serum beta-2 microglobulin concentration and 24-h urine beta-2 microglobulin concentration and excretion were higher in the isolated systolic hypertension than in the normotensive group ( P < 0.05). In isolated systolic hypertensive patients, 24-h urine beta-2 microglobulin concentration and excretion were related to ambulatory blood pressure ( r = 0.32–0.40, P < 0.05), but not to clinic blood pressure; waking systolic blood pressure had the strongest correlation with both 24-h urine beta-2 microglobulin concentration and excretion among derivatives of ambulatory blood pressure ( r = 0.35 and 0.40, P < 0.05). We conclude that ambulatory blood pressure, especially waking systolic blood pressure, is superior to clinical blood pressure in predicting renal function impairment, in isolated systolic hypertensive patients.