Abstract: Leaf morphological characters were investigated with the diallel analysis by using F1's among the five Hokkaido varieties. The additive gene effects predominated over the dominance effects in all characters. h (the total sum of the dominances of the loci) was significantly positive in the lengths of the second and third leaves, but was negative in the first leaf width. Two or more genes may affect to each character, as estimated with the one formula, (the maximum parent value - the minimum parent value)2/4D. Correlation coefficients among the characters indicated a trend that a short culm genotype had short, narrow and erect leaves, and vice versa.