Twenty cases of aortopulmonary window are reported with special reference to some unusual modes of presentation and hemodynamics. Patients over 15 years of age accounted for 35% of the group. This delayed presentation may relate to referral patterns and socioeconomic conditions prevalent in India. Curiously, this elderly subset had two modes of presentation—either as large left-to-right shunts with low pulmonary vascular resistance (71.4%), or as Eisenmenger's syndrome (28.6%). The reasons for the low pulmonary vascular resistance in the majority of these older patients remain unclear. The echocardiographic features of these defects can be missed in presence of significant associated cardiac lesions. A careful search should, therefore, be made for an additional aortopulmonary window in all cases with evidence of intercirculatory shunting.