An M mode echocardiographic study was performed, of left ventricular dimensions and wall thickness in two series of normal (N1, N2) and pathological (P1, P2) subjects. In the more recent series (N2 = 40, P2 = 17) data acquisition was facilitated by tests deduced from the technique of ultrasound transit time. The parameters compared were based on: 1) the proportionality between fractional shortening and fractional thickening (N1: not significant; N2: p less than 0.001), 2) the relationship between systolic radius and wall thickness (linear correlation, r = 0.95, between N2 and P2). The slope seemed to be related to the initial condition of contraction, the ratio of end diastolic wall thickness/radius (N1: p less than 0.01). There are several ways of normalising myocardial surface of section in adults and children; the normal surface is related to body surface area (r = 0.87; p less than 0.001 between calculated and predicted values for a N2 mean of 9.3 +/- 0.06 cm2/m2). The end diastolic diameters and wall thicknesses correlated with body surface area but the coefficients were not as statistically significant due to physiological variations in chamber filling. The indexed myocardial surface was increased (p less than 0.001) in the pathological series. The introduction of these tests improves the reliability of echocardiographic data. The use of several measurements simultaneously allows normalisation of body surface area and increases the diagnostic efficacy.