While previous studies highlight the dynamic nature of identity co-construction, how and especially why speakers construct and shift their own multiple identities still remains understudied. The present study argues that identity is part of speaker communicative resources as evidenced by radio program hosts’ strategic employment and shift among their different identities to facilitate their interactional purposes. Based on data drawn from radio medical consultations, this article attempts to reveal the dynamic adaptability of hosts’ identity construction. It is found that in (...) general, hosts of medical consultation programs construct three identities for themselves, namely an authoritative expert identity, a caring friend identity and a sales representative identity; the three identities constructed are respectively adaptable to power relationships, solidarity and role relationships between hosts and callers in conversation; the three identities shift in conversations to facilitate callers’ purchasing acts. (shrink)