In adults, calculation of left ventricular mass (LVM) has been shown to give higher values when based on M-mode measurements obtained by the second-harmonic imaging (SHI) technique than with the older fundamental imaging (FI) technique. No information is available in paediatric subjects. This study, therefore, compares LVM calculated from measurements obtained with SHI and FI in 14 children, aged 6.9-13.0 years. M-mode tracings were obtained in accordance with American Society of Echocardiography (ASE) recommendations. Three experienced sonographers performed measurements on each subject with both SHI and FI. The mean value was used in all calculations. LVM was calculated according to ASE convention and indexed by body surface area. LVM mean values were 58.9 +/- 9.7 g m(-2) for SHI and 57.8 +/- 8.2 g m(-2) for FI (P = 0.45). This preliminary study in a small group of paediatric subjects demonstrates no systematic differences between FI and SHI modalities in the calculation of LVM. The likely explanation is that the left ventricular endocardial border is usually well visualized with SHI as well as with FI in children.