Because of the concern about the ability of the morphologic right ventricle (MRV) to function over a long term as a systemic ventricle, adult patients with congenitally corrected transposition of the great arteries (CCTGA) were evaluated to determine the long-term function of the MRV. Morphologic right ventricular function was assessed by functional clinical classification and angiographic ejection fraction in 18 adult patients with congenitally corrected transposition of the great arteries. These patients had a mean age of 30.2 +/- 14.5 years (range 10 to 67 years). All but one had hemodynamically significant lesions, the most common being left atrioventricular valve regurgitation (11 patients), ventricular septal defect (seven patients), atrial septal defect (four patients), and pulmonic stenosis (three patients). The mean MRV ejection fraction at presentation was 55% +/- 11.5% (range 24% to 74%). Twelve of the 18 patients (67%) were followed clinically, with a mean follow-up time of 9.9 +/- 7.1 years (range 1 to 22 years). Eight were reassessed angiographically, with a mean MRV ejection fraction of 51.3% +/- 10.7% (range 30% to 67%). The other four were followed up clinically and evaluated by two-dimensional echocardiography, with normal MRV function in two patients. Eight of 12 patients (67%) were in functional class I at follow-up, one was in functional class II, one was in functional class III, and two had died. Our data suggest that the morphologic right ventricle can function appropriately over a long term in adult patients with congenitally corrected transposition of the great arteries.(ABSTRACT TRUNCATED AT 250 WORDS)