The present authors have used a replica method to obtain area size measurements for the apical foramen in 4,613 human permanent teeth, and have obtained the following results: 1. The morphology of the apical foramen is rich in variety which make it difficult to express its accurate size using foramen diameter measurement. It is therefore more appropriate to determine its size as an area measurement. 2. Much variation was observed in the size of the apical foramen even for teeth of the same type. It was, however, also observed that the foramen is smaller in smaller types of teeth and larger in larger types of teeth. It was also observed that, in teeth of the same type, those with a greater number of roots have smaller foramen than those with a smaller number of roots.