Red and green visual pigment genes were analyzed in color-normal Japanese males. DNA from 121 males was subjected to PCR-amplification for the promoter and exon 5 of these genes, and the products were sequenced with a PRISM 310 genetic analyzer (dye terminator). The number of visual pigment genes in each individual was estimated from the peak-heights of nucleotides on the sequencing electropherograms of the promoter; it was 2 in 46% (n = 56), 3 in 32% (n = 39), 4 in 12% (n = 15), and > 4 in 9% (n = 11) of the subjects. These numbers were similar to the ratios of green:red pigment genes obtained from the analysis of exon 5, suggesting the presence of a single red gene in each subject, except for one, N22. This subject was estimated to have 3 pigment genes: one red, one green, and one green-red hybrid. A more detailed analysis indicated that the first gene in N22 was the typical red one, the second gene was the green, and the third gene was the green-red hybrid. These results suggest that color-normal Japanese males who possess green-red hybrid genes are quite mle (<1%). (C) 2000 John Wiley & Sons, Inc. Col Res Appl, 26, S84-S88, 2001.