The frequent measurement and recording of arterial blood pressure are fundamental parts of patient monitoring in the intensive care unit and the operating room. Two major categories of techniques for measuring arterial blood pressures, non-invasive(indirect) and invasive (direct) methods are currently available. But many physicians often have an experience to recognize that there are some variances in arterial blood pressure data depending on the measuring techniques or personnels. In view of these points, we carried out this study to examine whether these variances of arterial blood pressures measured by Riva-Rocci cuff and Korotkoff sound method (indirect l), automatic non-invasive method (indirect 2) and arterial cannulation method (direct) and those measured by nurse and student nurse are statistically significant or not in 14 patients. The results were as follows. l) In contrast to statistically non-significant variances of diastolic and mean blood pressures among indirect 1, 2 and direct method measured by nurse, there was significant variance of systolic blood pressures between indirect l and direct method, 120±13 torr and 129±15 torr, retrospectively (p<0.05), 2) There were no statistically significant variances of systolic, diastolic and mean blood pres- sure between two indirect methods measured by nurse. 3) In contrast to non-significant variances among systolic blood pressure measured with an aid of indirect 1, 2 and direct method by student nurse, diastolic blood pressure by indirect 1, 88±l4 torr was significantly elevated as compared with those by indirect 2 and direct method, 79±l3 torr and 81±13 torr, retrospectively (p<0.05). 4) there was significant variance of mean blood pressures measured by student nurese between indirect 1 and 2 methods, l0113 torr and 94±13 torr, retrospectively (p<0.05). 5) there were significant variances between systolic, diastolic and mean blood pressures of 120±13 torr, 80±13 torr and 93±12 torr measured by nurse and those of l28±14 torr, 88±14 torr and 101±13 torr measured by student nurse, retrospectively (p<0.05).