Parents of pupils who were attending schools in a medium-size city in Japan were surveyed (n = 2381). Perceptions and attitudes towards people with intellectual disability were investigated. The prevalence of people with intellectual disability in the population guessed by respondents was very small (median = 5/1000). Almost half the respondents believed the prevalence rate of persons with intellectual disability in their own future family would be lower than that in the general population. Perceptions most strongly associated with attitudes were the estimated proportion of hereditary cause, and the possibility of having a person with intellectual disability in one's future family. Some important incorrect perceptions were based on wrong information and may be amenable to change by teaching. (Contains 1 table and 5 figures.)