Given the clear evidence that reducing blood pressure decreases the vascular complications of hypertension, loss of efficacy represents the principal complication of noncompliance with antihypertensive therapy. Withdrawal symptoms are also important and occur after abruptly stopping $-blockers and centrally-acting antihypertensive drugs, Very few studies have been conducted to assess the impact of missing 1 or 2 doses of an antihypertensive agent on short term control of blood pressure. A high trough to peak ratio (textgreater 50%) for a once-daily medication suggests a long duration of action. However, methodological problems in the design of the studies to determine trough to peak ratios make comparisons between various medications very difficult. In general, however, stopping a drug with a low trough to peak ratio is more likely to result in loss of antihypertensive effect than a drug with a high ratio. Poor compliance in dose-escalating studies with antihypertensive agents may have resulted in excessively high dose recommendations in clinical trials.