Purpose To clarify the care burden and associated factors among parents of adults with developmental disabilities in order to obtain suggestions for the family supports.Methods Subjects included 125 parents of adults (aged 18 or older) with developmental disabilities. All parents belonged to and/or contacted parents' associations, mental health welfare centers, and support centers for persons with developmental disabilities in the Tokyo metropolitan area. Participants completed self-report questionnaire surveys from October to November 2011. Questionnaire items included parent and adult demographic factors, parent care burden, disability state, and support available from family and others. The level of care burden was measured using the short Japanese version of the Zarit Burden Interview (J-ZBI_8).Results A total of 64 responses were analyzed. The mean J-ZBI_8 score was 12.8 (SD=7.2). Adults' most common diagnoses were autism (50%), Asperger's syndrome (25%), and pervasive developmental disorder (20%). state of daily life (P=0.041) and presence of secondary disability (P=0.001) were associated with parents' care burden in age-adjusted multiple linear regression analysis.Discussion Overall, the results suggest that it is important to assess developmental disability status and family support when developing programs to reduce parental care burden.