Atmospheric concentrations of carcinogenic asbestos fibers, have traditionally been measured visually using phase contrast microscopy. However, because this measurement method requires great skill, and has poor reproducibility and objectivity, the development of automatic counting methods has been long anticipated. We have developed the Asbestos Fibers Automatic Counting System (AFACS), and verified its accuracy via application to illustrations obtained from the Asbestos International Association (AIA). Important features of the AFACS system are as follows: (1) Counting criteria of the automatic counting system conform to those of visual counting. (2) The cost of the whole system is low because it is microcomputer-based.