Aortic valvular dilatation with a balloon catheter was performed in 44 patients, 20 men and 24 women, most of whom were very elderly (average age 77 years). The indication for valvular replacement had not been retained in these cases because of surgical contra-indications or a very high operative risk and in 3 cases because of patient refusal. Twenty-nine patients were in functional classes III or IV of the NYHA classification; 12 had syncopal episodes and 18 had invalidating angina. The dilatation was performed by a femoral arterial approach in 34 cases, and by a brachial arterial approach in 10 cases. MEDI-TECH catheters with 15, 18 or 20 mm diameters when inflated were used in the majority of cases. Several inflations lasting 10 to 240 seconds were performed in each case with balloons of increasing size. This was well tolerated in all but one patients who had a sharp syncope. The immediate results confirmed valvular dilatation. The average transvalvular pressure gradient fell from 76 +/- 25 mmHg to 30 +/- 13 mmHg (p less than 0.001). The aortic valve surface area calculated by the Gorlin formula increased from 0.5 +/- 0.18 cm2 to 1 +/- 0.42 cm2 (p less than 0.01). After dilatation the gradient was less than or equal to 40 mmHg in 37 cases; aortic valve surface area was greater than or equal to 1 cm2 in 14 cases and less than or equal to 0.7 cm2 in only 5 cases. The left ventricular ejection fraction increased immediately after valvuloplasty from 44 +/- 16 p. 100 to 49 +/- 15 p. 100 (p less than 0.01). In the 18 cases in which it was less than 40 p. 100 before valvuloplasty, it increased from 30 +/- 6 p. 100 to 36 +/- 9 p. 100 (p less than 0.02). Residual aortic regurgitation was only observed in one case. Two patients died in the hospital period (4.6 p. 100). There were no other serious complications. During an average follow-up period of 60 days (3 weeks to 6 months) there was a big improvement in symptoms in the great majority of cases and, in particular, syncopal and anginal attacks disappeared. Only 4 patients remained in functional classes III or IV after valvuloplasty. Percutaneous aortic valvuloplasty is a new, relatively simple, low risk, economic and very effective therapeutic procedure in all cases in which aortic valve replacement is contra-indicated or refused by the patient.(ABSTRACT TRUNCATED AT 400 WORDS)