Two hundred and sixty major apical foramina were examined stereomicroscopically to determine the contours of the apical foramen and the frequency of each shape. The observation was performed at 15 x magnification. During the examination the following shapes were observed: circle, ellipse, teardrop, number eight and irregular forms. Apical foramen most frequently had the circular shape and it was registrated in 58.8 per cent of the main root canal openings. The elliptic contour was presented in 22.7 per cent, the teardrop shape in 10.4 per cent and the shape similar to number eight occurred in 5.0 per cent of the samples. The statistical calculation revealed that the circular shape of the apical foramen is the most frequent finding (p less than 0.01). This finding seems to be optimistic in an attempt to perform the hermetic sealing of the apical foramen.