A system includes a durable portion with a durable housing and a separable disposable portion with a disposable housing that selectively engage with and disengage from each other. The disposable housing secures to a patient and may be disposed of after it has been in use for a prescribed period. Components that normally come into contact with a patient or with an infusion medium may be part of the disposable portion to allow for disposal after a prescribed use. A reservoir for holding the infusion medium may be part of the disposable portion, and may be supported by the disposable housing. The durable portion may include other components such as electronics for controlling delivery of the infusion medium from the reservoir, and a drive device including a motor and drive linkage.