It has been suggested that the maximal amplitude of the pulmonary valve motion following atrial contraction (Amax) may be useful in the clinical evaluation of patients with valvular pulmonary stenosis. To evaluate the specificity and sensitivity of this measurement in children, we reviewed the echocardiograms of the pulmonary valve of 120 subjects: 57 normal individuals, 25 patients with secundum atrial septal defect and without pulmonary hypertension, and 32 patients with pulmonary stenosis proven at catheterisation (mild in 16 patients, moderate in nine, and severe in seven). Amax ranged from 0 to 12 mm in the normal subjects, and from 2 to 16 mm in those with atrial septal defect. In mild pulmonary stenosis, Amax ranged from 2 to 12 mm, in moderate pulmonary stenosis from 2 to 14 mm, and in severe pulmonary stenosis, from 3 to 12 mm. Though mean Amax was significantly larger in patients with moderate and severe pulmonary stenosis compared with normal subjects, there was much overlap between the two groups so that individual cases could not be identified correctly from this measurement. No significant difference was observed when comparing Amax values of patients with atrial septal defect and those of patients with pulmonary stenosis of various severity, nor were any observed between the pulmonary stenosis groups. These findings indicate that Amax is neither specific nor sensitive for the presence or severity of valvular pulmonary stenosis in children, and that it cannot be used to evaluate non-invasively the results of pulmonary valvotomy.