Patterns and correlates of service utilization by adults with a developmental disability were examined using data from 831 mothers of an adult child with a developmental disability. A modified Andersen model of health services was used to examine service utilization in seven domains. Multinomial logistic regression revealed that predictors of services received as well as predictors of unmet need for services varied by service. Findings emphasize the importance of considering predisposing characteristics, enabling resources, and need as well as service in order to understand patterns of service utilization.