Since 1975, many studies have attempted to show that Type As are sympathetically hyper-reactive to environmental stimuli compared to Type Bs. Inconsistencies in findings have led Holmes (1983} to 2 challenge the basic assumption that a link exists between the Type A behavior pattern and processes which precipitate development of coronary heart disease. The present.study was an attempt to isolate the organismic variable psycho-physiologic reactivity and demonstrate through a replication-extension of Holmes, McGilley, and Houston (1984} that individual psycho-physiologic reactivity rather than the personality profile of Type A is predictive of heightened arousal due to challenge. Reactive and nonreactive Type As and Type Bs were selected from a pool of 136 male undergraduates. All were exposed to increasingly difficult levels of the WAIS digits recall backwards and block design tasks, during which heart rate, blood pressure, and electrodermal response were measured. Results show reactives evinced significantly higher systolic blood pressure across challenges compared to nonreactives. Types As and Bs did not differ in their physiologic responses to challenges.