Ambulatory blood pressure variability (ABPV) is a predictor of cardiovascular risk in hypertensives. Factors that contribute to ABPV are not well described. This pilot study aimed to investigate the relationship between ABPV and urine catecholamine metabolites in order to rationalise further therapeutic intervention in the management of hypertension. Twenty individuals (14 female), aged from 23 to 71 years, with primary hypertension were identified from referrals to a regional hypertension clinic. Individuals had a 24-h ambulatory blood pressure recording (Del Mar Reynolds), and a 24-h urine collection was analysed for metadrenaline and normetadrenaline by reverse-phase chromatography (Spherisorb ODS2) and electrochemical detection (Coulochem II). Normetadrenaline concentration correlated with systolic blood pressure (SBP) variability, r=0.493, P=0.02, and with SBP coefficient of variability, r=0.490, P=0.02. Metadrenaline concentration did not correlate with either SBP variability, r=0.177, P=0.43, or coefficient of variability, r=0.185, P=0.42. A correlation was observed between 24 h urinary normetadrenaline and measures of SBP variability but not 24 h urinary metadrenaline and blood pressure variability. It is hypothesised that sympathetic activity may influence SBP variability.