Normal M-mode echocardiography values were determined using computer-assisted measurements of echocardiograms (ECHO) in 202 children and young adults 25 days to 23 years of age: 77 were female, and 125 were male and, reflecting the population served by our Center, 99 were black and 103 were white children. The values for left and right heart wall thicknesses and chamber sizes were graphically displayed as a function of body surface area, and with an illustration of the regression line and 2 standard deviation (SD) range of normal for each parameter. In addition, normal ECHO predicting equations for dimension and function parameters were derived using multiple linear regression analysis with age, height, weight, sex, race, and heart rate as independent variables. A comparison was made between the observed data and the data derived from the normal predicting equations for each of the parameters. Also, values obtained from these equations were compared to data generated from other published normal predicting equations. A description of the digitizer measurements, computer interfacing, and a sample ECHO report form utilizing the predicted normal ranges for each of the parameters is presented. We propose that quantitative M-mode echocardiographic reporting should be easily accessible to all pediatric cardiology laboratories.