Index Mutual Funds (IMF) and Exchange Traded Funds (ETF) have developed into widely-accepted and fast growing passive investment instruments, offering investors a low-cost investment alternative in well diversified portfolios. Allocating more into IMFs and ETFs is the investors’ natural response to the experience with and the disillusion about actively managed investment performance. Despite these positive effects, this shift in fund allocation raises substantial concerns about possible negative effects on securities market trading and market quality, on corporate governance and product market competition as well as on systemic risk. Most research so far does not provide significant evidence of negative effects on market quality, on securities market trading, and on systemic risk. Whether the shareholdings of IMF ZBB 2016, 407and ETF providers reduces product market competition and whether the concentration of voting rights negatively effects corporate governance requires further analysis. Some problems may occur if ETF and IMF providers team-up with active investors. Overall, the introduction of IMFs and ETFs on broad market indices should be viewed as a financial innovation that broadens the investment spectrum providing many benefits to investors especially when viewed relative to the meager performance and performance persistence of actively managed mutual funds.