In young hypertensive patients, after a short period of abstention, caffeine ingestion has a significant pressor effect, although the acute cardiovascular responses have not been reported in elderly hypertensives. This study assessed the acute changes in BP, pulse rate, plasma renin activity (PRA) and arterialised plasma catecholamines after 250 mg of caffeine and matching placebo following 12 and 48 hours of caffeine abstention. After 48 hours caffeine abstention supine SBP was higher over the 120 minute study period following acute caffeine loading than following placebo (10 mmHg; 95% Cl 3-17 mmHg, P = 0.016) although the overall post-caffeine rise from baseline values was small (2 mmHg; -3 to 8 mmHg, P = 0.30). Similar differences were seen for supine DBP and standing SBP and DBP although pulse rate was unchanged throughout. After 12 hours abstention no acute pressor effect of caffeine was seen, in fact SBP fell over the study period (-5 mmHg; -10 to 0 mmHg, P = 0.05), and there was no difference between the caffeine and placebo phases. No change in plasma catecholamines or PRA values was found during any of the phases. These results suggest that in elderly hypertensives the pressor effect of caffeine (the equivalent of two to three cups of coffee) is small even after prolonged abstention. After the shorter abstention period, of the duration likely to be seen in clinical practice, no pressor response to caffeine was demonstrated. It is unlikely that acute caffeine ingestion has a significant effect on clinic BP measurements in elderly hypertensives who are regular caffeine consumers.