Ambulatory blood pressure (BP) monitors measure BP by oscillometric (Osc) or auscultatory (Aus) methods. In this study, we aimed to compare the values obtained by BP measurement methods in the ambulatory blood pressure monitoring (ABPM) device that can take measurements using both the methods, factors influencing these values, and their relevancy in obtaining valid measurement percentages. The study was conducted on 212 patients. BP values of these patients were measured with the Nissei DS-250 (Nihon Seimitsu Sokki Co. Ltd, Gunma, Japan) monitor capable of recording BP simultaneously by the Aus and the Osc methods. The cases, for which no records were obtained by any one of the two methods, were considered to have missing records. The impacts of age, sex, body mass index, and arm circumference on the valid BP measurement values were examined. The valid measurement percentage without any missing records obtained by the Osc method was 87.3 and 16% by the Aus method. The body mass index, age, and arm circumference did not affect this percentage. The 24-h BP measurement values were higher by the Osc method. The differences between both methods in systolic blood pressure and diastolic blood pressure were 3.8+/-4.6 and 2.3+/-2.7 mmHg, respectively. Although the Aus method yielded higher standard deviation values than the Osc method for systolic blood pressure, standard deviation values obtained by the Osc method were higher than those obtained by the Aus method for diastolic blood pressure. The percentage of obtaining valid measurements by the Osc method used in the Nissei DS-250 model ABPM device examined in this study is higher when compared with the Aus method. Therefore, while examining ABPM results, the Osc method may be preferable over the Aus method.