ECGs often are measured by digital sampling at uniform rates. With uniform sampling, no changes in the sampling rate are made in relation to the experimental content of the ECG. This study examined the question of which samples should be selected so that the most important information in an ECG is retained. The fan method of adaptive sampling was evaluated using 21,000 ECGs from 140 subjects, of age 2 days to 60 years, with normal and abnormal diagnoses. The fan method of adaptive sampling selects samples by determining where successive samples of a waveform fall in relation to a specified tolerance, and allows the longest possible line between selected samples as a function of the specified tolerance.