The $1.2 billion Fidelity Select Biotechnology Fund ( FBIOX) has a return of 18.6% this year and 37% over the past 12 months. The 95-stock fund has been managed by Rajiv Kaul since October 2005. The annual portfolio turnover is relatively high, at 119%, and 57% of its assets are concentrated in the top 10 positions. Its top holding is the biotechnology giant Amgen ( AMGN), which at 18.4% of the fund, is more than double the allocation of the next largest stock. Amgen has risen 9% this year. The company is a leader in biotechnology-based human therapeutics, with expertise in renal disease and cancer-care products. Alexion Pharmaceutical ( ALXN) is the second-largest holding, at 6.7% of fund's assets. Vertex Pharmaceutical ( VRTX), 6.5% of the fund, is up 58.6% this year. It is a developer of small-molecule drugs for the treatment of life-threatening diseases. It is close to commercializing telaprevir, a hepatitis-C treatment in late-stage development with the potential to achieve blockbuster status, according to Morningstar analysts. The fourth-largest position is Biomarin Pharmaceutical ( BMRN), at 4.5% of the fund. The company, which is building a portfolio of genetic disease therapeutics, many used in the treatment or rare diseases, is up 2% this year.