Respondents' experiences most frequently reported in open-ended descriptions of their forming perceptions of persons with intellectual disability were "passive" experiences, such as coming across them as a stranger in one's town. These were generally not associated with positive attitudes. Formation of positive attitudes mainly derived from experiences such as having a person with intellectual disability in the family, or knowing someone who has a family member with intellectual disability. Another experience associated with positive attitudes was having awareness that anyone could have a person with intellectual disability in his/her family. An unpleasant experience with a person with intellectual disability, especially in childhood, was strongly associated with negative attitudes. Interestingly, most respondents (even those who were in the bottom quartile of attitude scores) believed that they had a more tolerant attitude to disability than the average person. (Contains 5 figures.)