Left atrial (LA) and right atrial (RA) volumes were calculated from two-dimensional echocardiography (2D echo) in 54 normal volunteers, of whom 23 were nonathletic men and 25 nonathletic women; 6 additional men had a history of athletic training. Ages ranged from 20 to 66 years (average nonathletic group, 38 years; athletic men, 28 years). The LA volume was measured by single-plane area-length algorithm from apical 2-chamber (2CH) and 4-chamber (4CH) views and from their combination by means of Simpson's rule. The RA volume was analyzed only in the 4CH view. Mean LA volume was larger for men than women; for nonathletic men, 46 +/- 14 ml for 2CH view and 38 +/- 10 ml for both the 4CH view and for Simpson's rule combination of the apical views. For women it was 36 +/- 11 ml for the 2CH view, 34 +/- 12 ml for the 4CH view, and 32 +/- 10 ml by Simpson's rule. Right atrial volume was 39 +/- 12 ml in nonathletic men and 27 +/- 7 ml in women. In the six athletic men, LA volume and volume index, but not RA volume and volume index, were significantly larger than in nonathletes. These findings in this small sample suggest that caution should be exercised in interpreting atrial enlargement in athletes. There were no significant correlations between atrial volumes and age, although individuals over 65 years with normal hearts were not represented. In evaluating LA volume in a given patient, it is advisable to use specific values for each apical view and algorithm and to correct for either sex or body surface area (BSA) but not for both. In the RA it is necessary to correct for both sex and BSA.