By means of a planimeter and skulls adjusted in the eye-ear plane, measurements of areas of the foramen ovale, spinosum, lacerum, jugulae and orifice of the canalis caroticus on both sides of the external surface of the skull base have been taken on 100 adult skulls collected in Chengdu. The symmetry of these areas has been studied. The main results of the study are given below: 1. In 4% of the whole series, the area of the foramen ovale is approximately equal on the two sides and the difference in area between the two sides is less than 1%. In 44%, the right side is larger, and in 52%, the left is larger. 2. In 5% of the whole series, the area of the foramen spinosum is approximately equal on the two sides. In 42%, the right side is larger, and in 53%, the left is larger. 3. In 4% of the whole series, the area of the foramen lacerum is approximately equal on the two sides. In 46%, the right side is larger, and in 50%, the left is larger. 4. In 3% of the whole series, the area of the foramen jugulae is approximately equal on the two sides. In 76%, the right side is larger, and in 21%, the left is larger. 5. In 3% of the whole series, the area of the anterior part of the foramen jugulae is approximately equal on the two sides. In 50%, the right side is larger, and in 47%, the left is larger. 6. In 17% of the whole series, the area of the intermediate part of the foramen jugulae is approximately equal on the two sides. In 37%, the right side is larger, and in 46%, the left is larger. 7. In 2% of the whole series, the area of the posterior part of the foramen jugulae is approximately equal on the two sides. In 79%, the right side is larger, and in 19%, the left is larger. 8. In 5% of the whole series, the area of the orifice of the canalis caroticus is approximately equal on the two sides. In 58%, the right side is larger, and in 37%, the left is larger. Moreover, a quantitative analysis of the bilateral areas has been carried out. The foramen area is highly positive in correlation With the product of its length and width. Therefore, the regression formulas of the areas are as follows: The foramen ovale-right, ■=1.5129+0.6699x (r=0.9417); left, ■=0.3695+0.6876x(r=0.8949). The foramen spinosum-right, ■=0.7827+0.6089x (r=0.8755); left, ■=0.3499+0.6695x (r=0.9207). The foramen lacerum-right, ■=9.4190+0.4480x (r=0.9147); left, ■=13.5198+0.4082x (r=0.8493). The foramen jugulaeright, ■=18.3913+0.5092x (r=0.8843); left,■=11.3561+0.5744x (r=0.9193). The anterior part of the foramen jugulae-right, Y=3.3141+0.4858x (r=0.8330); left, ■=3.2294+0.4854x (r=0.8452) The intermediate part of the foramen jugulae-right, ■=2.5434+0.4311x (r=0.7942); left, Y=1.7547+0.5227x (r=0.8366). The posterior part of the foramen jugulae-right,■=1.3470+0.6311x (r=0.8273); left, ■=0.9110+0.6586x (r=0.9480). The orifice of the canalis caroticus-right, ■=1.0986+0.6794x (r=0.9128); left, ■=1.5038+0.6590x (r=0.9219). (x is the product of the length and width of its foramen).