Our aim was to determine, using a computer program for measurement and analysis, the effects, if any, of age and gender on the electrocardiographic measurements in a large cohort of Turkish children. We analyzed standard simultaneous 12-lead electrocardiograms from 2241 healthy Turkish children, aged from 1 day to 16 years, to calculate limits of normality of a variety of electrocardiographic measurements for 12 age groups. Cinically significant differences were shown to exist, and the results compared with previously established normal limits. Differences were demonstrated for gender in measurements of both amplitude and duration, particularly in the adolescent period. We have provided tables and figures showing age and gender-dependent means and upper limits of normal electrocardiographic parameters for the important leads.