The physiological variations of blood pressure are exhaustively reviewed. Effects of age, sex, the type of artery on which it is recorded, posture, basal conditions, meal, tobacco, exercise, fasting constitution, cooperation and race on blood pressure have been discussed. It has been found that in general systolic blood pressure showed a fall ranging between 2mm and 25mm when posture is changed from lying to sitting. The diastolic pressure also showed a fall in majority of the cases examined ranging between 2mm and 15mm. Tables in respect of factors affecting the blood pressure have been adequately provided.