This study investigated Type A behavior in preschool children and its relation to cardiovascular reactivity. One hundred forty-four children from 3.5 to 6.5 years old were categorized by their teachers according to the Matthews Youth Test for Health (MYTH) as Type A, Mixed, or Type B. The children's pulse, pulse rate variability, and blood pressure were then measured at rest and during a challenging situation. Analysis of covariance indicated that Type A children showed a significantly greater systolic rise to challenge than did Type B children, a finding similar to that of adults and one which might be thought of as a logical precursor to adult cardiac disease. (Author)