The physician is an important gatekeeper in the "buying" process for many health care services. Consulting physicians and tertiary care hospitals depend on physician referrals for much of their patient volume. A field survey of more than 1,000 physicians uncovered their attitudes and choice criteria pertaining to referrals. Physician referral attitudes are used as a basis for creating four physician segments. The authors explore attitude and behavioral differences among the four segments and discuss several physician marketing implications.