The $768 million Fidelity Select Medical Delivery Fund ( FSHCX) leads all equity funds with a 24% return this year through May 9, according to a Morningstar ranking. It has a 39% return over the past 12 months, but it should be noted that the fund lost 44% of its value in 2008 when the stock market collapsed. Select Medical Delivery's volatility is due to its narrow agenda: Managers may invest only in health insurers, hospitals and other health-services providers. The fund, which comprises 64 holdings, has been managed by Andrew Hatem since February 2009. Medco Health Solutions ( MHS), the nation's largest pharmacy-benefits manager through its mail-order pharmacy and network of retail pharmacies, is the fund's largest holding at 10%. Medco's shares are up 4.9% this year. Express Scripts ( ESRX), at 8.9% of the fund's assets, is the No. 2 position. The company competes directly with Medco. UnitedHealth Group ( UNH) makes up 7% of Select Medical Delivery. The company's stock is up 40% this year. UnitedHealth, with 77 million subscribers, offers risk-based health insurance, non-risk-based plan management for self-insured employers, Medicare and Medicaid plans, pharmacy benefits and database and consulting services. Its subsidiaries include UnitedHealthcare, OptumHealth and OptumRx. One of the hottest performers for the fund is Healthspring ( HS), up 65% this year. The company is a Medicare-focused managed-care organization that provides health benefits to 162,000 subscribers throughout Tennessee, Texas, Alabama, Florida, Illinois and Mississippi.