Fertile Japanese isolates of P. oryzae were mated with the most fertile hermaphroditic isolates from ragi, Eleusine coracana, by using the 3-points culture method. The hermaphroditic tester lines (mating type A or a) produced perithecia with either white beaks or black beaks, when mated with an isolate of opposite mating type. Each monoconidial isolate from ragi or rice was crossed with the A and a tester lines by inoculating them at 3 points on a Misato-Hara medium. Matings between compatible hermaphroditic tester lines produced 2 bands of perithecia. Each isolate produced its own band of perithecia on its own side. Some additional isolates from ragi functioned as hermaphrodites, but most functioned only as males. In crossings between a compatible tester line and an isolate functioning as a male, 1 band of perithecia was produced on the side of the tester line. None of the crosses between 2 isolates from ragi functioning as males, even between A and a, was fertile. Crossing between every isolate from rice and a compatible tester line produced only 1 band of perithecia on the side of the tester line. Fertile isolates of P. oryzae collected from rice in Japan could only function as males.