The study population included 51 patients, aged 34-67 years with essential arterial hypertension treated with 3-5 hypotensive drugs at the Outpatient Antihypertensive Department. Based upon frequent measurements of elevated arterial blood pressure values they were found to be therapy resistant. 24-h ambulatory blood pressure monitoring recorded at one hour intervals (Space Labs) excluded 8 patients (15.7%) from the resistant hypertension group as the number of values > 140/90 mm Hg did not exceed 25% of the measurements. In these patients white coat hypertension was the reason for diagnosing resistance. In 18 patients (35.3%) the initial diagnosis was confirmed as the number of increased values was 80-100%. The severity of eye fundus changes, higher blood pressure values and male predominance characterized the resistant group. The use of long-term noninvasive automatic blood pressure recording helps us to exclude pseudo-resistance and avoid further intensification of treatment.