BACKGROUND Although 3-dimensional echocardiography (3DE) has been applied during dobutamine echocardiography it has not been used during exercise echocardiography. We sought to compare feasibility and accuracy of 3DE and 2-dimensional echocardiography (2DE) during exercise echocardiography. METHODS 100 patients underwent peak and postexercise (PEx) 2DE and 3DE on separate days. Coronary artery disease was detected in 58 patients. A quality score was calculated by assigning 0 to 3 points to each wall (apicoseptal, posterolateral, anterior, inferior). RESULTS Feasibility of peak 2DE, peak 3DE, PEx 2DE, and PEx 3DE was 99%, 92%, 100%, and 95%, respectively (2DE at peak or PEx vs peak 3DE, P < .05). Agreement between 2DE and 3DE was 82% at peak (kappa = 0.62) and 78% at PEx (kappa = 0.55). Quality score less than 2 was seen in 4% of the walls with peak 2DE, in none with PEx 2DE, in 18% by peak 3DE, and in 14% by PEx 3DE. The mean quality score was lower with 3DE at peak and at PEx (2.4 +/- 0.9 vs 2.9 +/- 0.3; and 2.5 +/- 0.8 vs 3.0 +/- 0.1, both P < .0001). Acquisition time was shorter with 3DE at peak and PEx (22 +/- 8 vs 43 +/- 14 seconds; and 15 +/- 5 vs 31 +/- 14 seconds, both P < .0001). Sensitivity of peak 2DE, peak 3DE, PEx 2DE, and PEx 3DE was 84%, 78%, 71%, and 58%, respectively (P < .05 vs peak 3DE and peak 2DE). Specificity was 76%, 73%, 93%, and 88%, respectively. Accuracy for peak 2DE was 81% (area under the curve [AUC] 0.81, 95% confidence interval [CI] = 0.71-0.91); for peak 3DE was 76% (AUC 0.76, 95% CI = 0.65-0.86); for PEx 2DE was 80% (AUC 0.84, 95% CI = 0.75-0.92); and for PEx 3DE was 71% (AUC 0.73, 95% CI = 0.62-0.83). CONCLUSIONS Three-dimensional echocardiography during exercise is comparable with 2DE in terms of sensitivity and specificity but feasibility is lower.