In this chapter we examine the three main types of mutual funds, open end funds, closed end funds and exchange traded funds. After a description of each of these organizational forms, we discuss the principle research issues for each type. For open end mutual funds, this includes performance measurement techniques, how well funds have performed, and the informational content of past performances, how well investors do in selecting funds, and the determinants of cash flows into funds. For closed end funds, we discuss determinants of the discount and why this organizational form exists. Finally ...