Multimorbidity may be related to the supposed early aging of people with intellectual disabilities (ID). This group may suffer more often from multimorbidity, because of ID-related physical health conditions, unhealthy lifestyle and metabolic effects of antipsychotic drug use. Multimorbidity has been defined as two or more chronic conditions. Data on chronic conditions have been collected through physical assessment, questionnaires, and medical files. Prevalence, associated factors and clusters of multimorbidity have been studied in 1047 older adults (>= 50 years) with ID. Multimorbidity was prevalent in 79.8% and associated with age and severe/profound ID. Four or more conditions were prevalent in 46.8% and associated with age, severe/profound ID and Down syndrome. Factor analyses did not reveal a model for, disease-clusters with good fit. Multimorbidity is highly prevalent in older adults with ID. Multimorbidity should receive more attention in research and clinical practice for targeted pro-active prevention and treatment. (c) 2014 Elsevier Ltd. All rights reserved.