For many years the significance of transient hypertension has been a topic of discussion. As long ago as 1921 Fahrenkamp1and Kylin2independently noted that excessive variability of the blood pressure, with temporary rises above the usual normal, sometimes was found in the early stages of hypertensive vascular disease. A little later Fahrenkamp3stressed the importance of psychic disturbances as a cause of such vasomotor instability. More recently, numerous authors have presented data in support of the view that transient elevations of blood pressure, induced by emotion or some other stimulus, should be regarded as evidence of a possible prehypertensive state.4But the number of cases studied has been relatively small, the periods of observation usually have not been long and no records have been kept between their beginning and end. Inferences drawn from insurance statistics are based almost entirely on mortality experience following a single