The aim of the study was to investigate the effects of the cylooxygenase (COX)-2 specific inhibitor, rofecoxib, on blood pressure (BP) and heart rate (HR) in patients with well-controlled hypertension and osteoarthritis via 24-h ambulatory monitoring. Thirty patients with well controlled hypertension were included. Fifteen patients had osteoarthritis and were recommended by their rheumatologists to take rofecoxib 12.5 mg/ day (rofecoxib group). The control group consisted of 15 patients who had hypertension but no clinical osteoarthritis and did not receive any anti-inflammatory drugs. Twenty-four-hour ambulatory monitoring of BP and HR were performed on the day before initiation of rofecoxib therapy and on days 3 and 14 of COX-2 therapy The control group underwent 24-h monitoring three times at similar intervals. Antihypertensive medications were continued. On day 3 of rofecoxib therapy, mean HR for both daytime and nighttime were lower than those at baseline. On day 14, the changes in mean HR did not differ from baseline values. Similarly, diastolic BP (daytime and nighttime) on day 3 appeared to be lower than at baseline. However, this difference was not observed on day 14, and mean daytime and nighttime diastolic BP returned to baseline values. There was no statistically significant difference in the mean arterial pressure or systolic BP recordings on days 3 or 14 than at baseline. Rofecoxib 12.5 mg/day did not significantly increase BP during 24-h ambulatory BP monitoring in patients with well-controlled hypertension and osteoarthritis.