The purposes of this study were to find out correlations between developmental disorders and blood type factors. Blood type factors examined in this study were ABO blood type and RH blood type for children and parents. The subjects were 221 children with disability and their parents, and 542 children without disorders their parents. The questionnaire was composed of 6 items related in ABO blood type and RH blood type for children and parents. The results of this study were as follows: First, there were no significant differences among fathers, mothers, and children of two groups in the distribution rate of ABO blood type, but there were significant differences between parents of two groups in he distribution rate of RH blood type. Second, there were no significant differences between children of two groups in the distribution rate of RH blood type. Third, mother-children correlations were higher than father-children correlations in two groups. Fourth, there were no significant differences in the rate of having the same father-mother ABO blood type between two groups. Fifth, developmental disability group was higher then general group in the rate of having father-mother-children different RH blood type. seventh, general group was higher than developmental disability group in the rate of marrying between father-mother with RH- blood type. The results of this study suggest that there are correlations between developmental disorders and RH blood type of parents.