Assessment of control of hypertension by some authors has revealed that optimal blood pressure control is not yet achieved in many of those that are on treatment. Resistant hypertension, plays a part as one of the factors responsible for this poor control state. Because of the peculiar problems posed by this group of hypertensives, we assessed the burden and factors responsible for resistant hypertension among hypertensive subjects attending the Medical Outpatient Clinic of the University College Hospital, Ibadan, Nigeria. Resistant hypertension was defined as blood pressure [symbol: see text] 140/90 mmHg in the presence of use of a combination of three antihypertensive drugs, including a diuretic at near maximum doses for at least one month. Five hundred and sixty-six consecutive subjects (218 males and 348 females) with a mean age of 56.0 +/- 14.3 years were screened for resistant hypertension. One hundred and forty-four (mean age 54.55 +/- 15.1 years), were fully controlled with a blood pressure of 120 +/- 9/77 +/- 2 mmHg. 394 men age of 56.7 +/- 11.7 years had non-resistant hypertension with blood pressure of 167.5 +/- 23/102.3 +/- 1.2 mmHg. Only 28 (5%) of the whole study group (mean age 51.8 +/- 9.7 years) were found to have resistant hypertension with a blood pressure of 176.4 +/- 43/109.6 +/- 14.8 mmHg. The subjects with resistant hypertension were significantly younger than those with non-resistant hypertension P < 0.02. There was no significant difference between their systolic blood pressure (P > 0.3) whereas; there was a significant difference between their diastolic blood pressure P < 0.002. Among those who had resistant hypertension, non-compliance was documented in 14 (50%) while it was in 73 (18.5%) of those without resistant hypertension P < 0.00053. Alcohol, tobacco, Obesity, use of non-steroidal anti-inflammatory drugs and excessive use of salt were not found as key factors responsible for resistant hypertension in this study.