AIMS: Real time full-volume 3D echocardiography (3DE) allows rapid and noninvasive measurement of left (LA) and right atrial (RA) volume without geometric assumptions. Different algorithms from different commercial providers are available. Older software requires manual tracing of endocardial contours. Recently, software with semiautomatic endocardial contour-finding algorithms has become available, which considerably speeds up the procedure. Our aim was to compare, in the same dataset, both LA and RA volumes determined by an algorithm involving manual tracing to the corresponding volumes obtained by an algorithm with semiautomatic contour detection. METHODS: Maximal atrial volumes were measured in 88 patients using a multiplane interpolation method algorithm based on manual planimetry of 8 slices. These volumes were compared with volumes determined by the QLAB 8.1 software using semiautomatic border detection. RESULTS: Linear regression showed excellent correlation between volumes determined by manual and by semiautomatic software for both LA and RA (r(2) = 0.90 and 0.89, respectively, P < 0.001). Bland-Altman analysis of manual versus semiautomatic volume determination showed narrow 95% limits of agreement (-15.9 to +12.0 mL for LA volume and -13.9 to +12.2 mL for RA volume) with a minimal bias of -1.9 ± 7.0 mL and -0.8 ± 6.5 mL, respectively, by the semiautomatic method. CONCLUSION: The semiautomatic border detection method shows excellent correlation for maximal LA and RA volume determination compared to the more time-consuming, multiplane interpolation method, with only slight underestimation. The results indicate that values of LA and RA volumes obtained by either algorithm can be compared, for example, during follow-up examination