Ambulatory blood pressure (BP) levels were assessed and types of activities were recorded every 20 min for a 12-hr period in 131 normotensive or mild-moderate hypertensive subjects. Systolic (S)BP and diastolic (D)BP levels varied significantly as a function of the social situation (alone, with family, with friends, or with strangers). BP levels were lowest when subjects were with family and were highest when subjects were with strangers.