As echocardiography is being used more often, its value and accuracy are becoming more fully appreciated, especially for identifying normal anatomic variants and their possible erroneous interpretation as pathologic states. We report the echocardiographic and clinical findings observed in sixteen subjects examined at our Cardiological Service in the period from January 1987 to April 1988. Mean age of these subjects is 40 +/- 27.04. Of these subjects, six are affected by other cardiac pathologies and ten are unaffected (Group A). First, we describe in all the patients M-mode and two dimensional patterns of persistence of the right venous sinus valve known as the Chiari network. This structure can present as a highly mobile, highly reflective echo target, which can be seen especially by means of the bi-dimensional technique. The Chiari network could be seen with all four standard approaches. The two most diagnostic views are, in our experience, the short axis parasternal view (62.5%), and the subcostal view (87.5%). In a great number of subjects (75%) the Chiari network could be seen in at least two approaches. Second, in Group A we make a clinical examination. Nine subjects in this group show the presence of a cardiac systolic murmur with vibratory characters from grade 1/6 to grade 3/6. 50% of the same patients presented supraventricular arrhythmias (particularly, two presented reciprocating paroxysmal supraventricular tachycardia and one paroxysmal atrial fibrillation). The significance of these findings is not clear yet. We, at least, emphasise that the Chiari network could be confused with other curvilinear highly mobile, echo targets such as right-heart vegetations, flail tricuspid leaflets, a small right-heart thrombus or even a pedunculated right heart tumor (especially right atrial myxoma). On the contrary, this structure might be considered a "normal anatomic variant".