In a previous study we showed that the Gorlin formula for measuring the valve areas in patients with stenotic mitral or aortic valves can be simplified without loss of accuracy. The simplified formula states that the valve area is equal to cardiac output (liters/min) divided by the square root of the pressure gradient across the valve. In this study we compare the Gorlin formula and the simplified formula in measuring the valve areas in 12 patients with congenital pulmonic stenosis. There was an excellent correlation between the two methods (r = 0.98 y = 0.07 + 1.16 X, P less than 0.001). Therefore the simplified formula can be used in measuring the severity of pulmonic stenosis. This method is simpler and easier to memorize than the Gorlin formula.