Design: Three-arm randomized clinical trial. Setting: Large hospital with community and trainee physicians. Population: 306 enrolled patients with complex medical histories. Interventions: In one intervention arm, pharmacists, and in the second intervention arm, pharmacy technicians obtained initial AMHs prior to admission. They obtained and reconciled medication information from multiple sources. All arms, including the control arm, received usual AMH care. This included common process variation occurring in: accuracy of pre-existing medication histories; nurses' ability to obtain AMHs at hospital admission; and admitting physicians' efforts to verify and order from prior AMHs.