The frequency, morphology, symmetry and asymmetry of the retro-articular process of the human temporal bone are studied in 811 adult skulls, being 386 from whites (301 men and 85 women), 245 from Negroes (137 men and 108 women), 138 from mulattoes (94 men and 44 women) and 42 from Japanese (31 men and 11 women). In 1,591 out of the 1,622 observations there was an evident retro-articular process. It was classified according to its shape as mam-millary, pyramidal, tubercular, crest-like or molar. Furthermore, in each one of these above referred types the process showed to be large, middle or small in size. The author states that in 98.4% of the skulls studied an evident retro-articular process could be observed; it was symmetrical in 790 cases, asymmetrical in 713 cases. These results are against the literature on the subject because it has been stated that in the present-day man the retro-articular process is very rare and, when present, usually very small.