Ambulatory blood pressure monitoring (ABPM) devices are increasingly being used in the assessment of hypertension. The purpose of the study was to investigate patient's diurnal BP variation and to further determine the differences of BP readings between male and female patients and the effects of age in patients who attended the clinic with essential hypertension. In addition, evidence of relationship between the parameters recorded by 24-hour ABPM was also investigated. This study was conducted in an outpatient specialist clinic. Two indices were used to demonstrate the diurnal BP variation. Firstly, the diurnal systolic blood pressure (SBP) and diastolic blood pressure (DBP) variations which were calculated as night/day BP ratio for SBP and DBP respectively. Anyone scoring less than 100% were categorised as dippers. Secondly, nocturnal falls in SBP and DBP were calculated as (awake SBP-sleep SBP)/awake SBP x 100 and (awake DBP-sleep DBP)/awake DBP x 100 respectively. The results showed that there was no significant difference in the mean BP between male and female patients. In general, the study sample were categorised as dippers and non dippers. There were more male dippers than female dippers. Finally correlation analysis revealed that age is related to SBP variables whilst night HR showed positive correlation with night time BP. It is concluded that ABPM was shown to be a useful tool to analyse the variation and prevalence of cardiovascular risk markers in hypertensive patients and can easily be done in an outpatient set-up.