Adults with ID/DD live in increasingly small community settings, where the risk of loneliness may be greater. We examined self-reported loneliness among 1,002 individuals with ID/DD from 5 states in relation to community residence size, personal characteristics, social contact, and social climate. One third reported being lonely sometimes and one sixth said they were often lonely, but loneliness was not more common for people living alone or in very small settings. More loneliness was reported by residents of larger community living settings of 7 to 15 people. More social contact and liking where one lives were associated with less loneliness. Social climate variables, such as being afraid at home or in one's local community, were strongly associated with greater loneliness.