Diversified Pharmaceutical Services entered the market in 1976 as the pharmacy benefit manager for United HealthCare (now United HealthGroup), a leading national managed care organization. Diversified pioneered many cost containment strategies that are now core PBM services and became a recognized leader in clinical programs. After its acquisition by SmithKline Beecham in 1994, Diversified played a pivotal role in that company's Healthcare Service division. Express Scripts acquired Diversified April 1, 1999 and consolidated its position as a leading PBM for managed care organizations.