In order to determine the geographical distribution of Ancylostoma duodenale and Necator americanus in Taiwan, 2,759 fresh stool samples were collected from 5th-grade school children of both sexes among 43 preliminary schools in 16 counties, and then examined by means of the modified test-tube filter-paper cultivation method for identification of the filariform larvae of hookworm. Both species of A. duodenale and N. americanus are widespread in Taiwan. The overall infection rate was 20.00%. The rate of A. duodenale, N. americanaus and mixed infection of both species was 9.85%, and 7.75% and 2.39% respectively. Geographically, N. americanus (12.64%) predominated over A. duodenale (5.43%) in the north (Ilan, Taipei, Taoyuan, Hsinchu and Miaoli) and the east (Taitung) areas. On the contrary, A. duodenale (13.40%) predominated over N. americanus (5.63%) in the central (Nantou, Taichung, Changhua and Yunlin), the south (Chiayi, Tainan, Kaohsiung and Pingtung) and the east (Hualien) areas. On the other hand, the rate of infection on the offshore island (Penghu) was much lower (1.19%) than the others (21.10-21.29%).