The primary aim in the surgical management of heart disease is an accurate diagnosis. This is achieved by a thorough clinical examination combined with the appropriate special investigations. For convenience, we think in terms of congenital and acquired conditions although the distinction is not always clear. Congenital lesions can usually be subdivided according to the presence or absence of cyanosis. There is also an important intermediate group of conditions which may develop cyanosis on exer­ tion or exercise. In the group of acyanotic lesions it is convenient to divide cases into those with and without a left-to-right shunt. This subdivision is made mainly on the radio­ graphic appearances of the lung fields. The following simple classification will be found helpful in narrowing the diagnostic possibilities in an individual case - Surgical Classification of Heart Disease Cyanotic Congenital Intermittent Heart Disease Cyanosis { Obstructive Lesions Acyanotic { L-R Shunts (lung fields) Endocardium (valves) Myocardium Pericardium Major blood vessels Such a classification cannot hope to be comprehensive but the main groups are covered including the majority of surgically treatable conditions. The major vessels leaving and entering the heart can conveniently be considered in relation to heart disease since coarctation and ductus arteriosus have long since been re­ garded as congenital cardiac surgical problems.