We present three hearts showing right atrial outlet atresia with straddling left atrioventricular valve; clinical data of two of the patients are reported. For semantic and practical reasons we believe the terms tricuspid or mitral atresia should not be used in these cases, and atrial outlet atresia is preferable; for similar reasons we prefer to use stradding left or right atrioventricular valve. These anomalies represent an interesting form of double outlet atrium and diagnosis clinically may be possible if the existence of the anomaly is considered. Differentiation from common atrioventricular canal with atrial outlet atresia is important since total repair, which is possible for this last anomaly, does not seem feasible in cases like ours. Classifications of tricuspid atresia may have to be enlarged to include cases with double outlet from either ventricular chamber or anatomically corrected malposition. Characterisation of the right ventricular chamber is difficult; we believe that description of its morphology and the type and mode of its connections should be used.