Surface electromyography and latency of return to relaxation baseline of the frontalis muscle as well as systolic, diastolic and mean arterial blood pressure were assessed in 100 subjects. Significant positive correlations between such electromyographic measures and blood pressure values were obtained. The theoretical and practical relevance of these findings are discussed in relation to the search for a direct relaxation factor and the construction of more efficient relaxation techniques in the behavioural treatment of essential hypertension.