BACKGROUND Abundant appearance of late potentials registered by high resolution ECG (HR-ECG) has been shown to predict a risk for cardiac arrhythmia. The aim of this study was to evaluate the appearance of normal and abnormal late potentials in a group of Finnish private and commercial pilots. METHODS Standard 12-lead ECG and 40-250 Hz band-pass filtered HR-ECG were recorded in 168 healthy male pilots. The following parameters were estimated: the root-mean-square voltage in the terminal 40 ms (RMS40), the total filtered QRS duration (FQRSD) and the duration of terminal high frequency low amplitude signal (HFLAD) of less than 40 microV in the filtered QRS. RESULTS Age (38 +/- 12 yr) and height (179 +/- 6 cm) had a significant (p < 0.005) and independent association with the total filtered QRS duration. No such correlations were observed for RMS40 or HFLAD. Mean +/- SD for RMS40 was 35.3 +/- 15.4 microV, for FQRSD 114.6 +/- 6.8 ms and for HFLAD 31.0 +/- 7.9 ms. Smokers tended to have longer late potentials (HFLAD) than non-smokers. Fasting blood glucose had a significant (p < 0.05) positive correlation with HFLAD. Serum cholesterol level had no correlation with the HR-ECG parameters. Age and height of the subject were associated with the total QRS duration as follows: FQRSD (ms) = -9.7* log age (yr) + 0.2*height (cm) + 94.6.