The aim of the study: the assessment of reproducibility of some chosen parameters obtained in 24-hour ambulatory BP monitoring (ABPM) with special focus on the morning blood pressure surge (MS) Additional goal: finding out which clinical parameters affect reproducibility. The examination was held in a group of 92 patients (55 people with hypertension and 37 healthy volunteers.) The ABPM measurement was taken thrice.MS was estimated on the basis of four definitions taken from the world literature: sleep-through MS, preawake MS, Bilo MS i Wizner, Zimmer-Satora MS.The results:- reproducibility of basic parameters obtained in ABPM record i.e. 24-hour blood pressure (BP), diurnal and nocturnal BP is very high.- reproducibility of office BP is poorer.- reproducibility of 24-hour BP variability and the day-night reduction of BP is poor.- MS is poorly reproducible - the best reproducibility was observed in the group of normotensive people. In the whole population and in the group of hypertensive patients, the best reproducibility was observed for Wizner, Zimmer-Satora MS.- reproducibility of MS estimated on all four definitions is affected by 24-hour systolic BP variability and, in case of Wizner, Zimmer-Satora MS, by 24-hour HR variability.- neither the white coat effect nor office BP affect MS reproducibility.