Within the framework of the CETUS challenge, forty-five 3D echocardiographic datasets have been acquired and segmented independently by three clinical experts from different hospitals. The goal was to generate a well-established ground truth of validated expert contours on this broad range of images from different ultrasound vendors, for a number of common pathologies. Image data were acquired and segmented according to a specifically designed protocol. Since there is no clear standard or guideline for segmentation for 3DUS, we defined a tracing consensus which results in clinically acceptable and reproducible contours. Tracing was performed in four longitudinal and five transversal 3D-derived 2D planes in ED and ES. 3D contours were constructed from these tracings. If the contours or their clinical parameters differed by more than a predefined level, the tracings were compared and the experts would reach a consensus interpretation on the best segmentation. One or more experts would then adapt their tracings. Final distance differences in contours were 0.77±0.18mm for the training set and 0.82±0.27mmfor the testing set. For the training set, 69% of contours were retraced. For the testing set, 76% of contours were retraced. The used protocol resulted in well-established ground truth contours.