This article will concern itself with the various techniques for selecting portfolios of securities. It should be made clear at the outset that a good portfolio is not just an amalgamation of a number of “good” stocks and bonds. Rather, it is an integrated whole, each security complementing the others. Thus, the investment manager must consider both the characteristics of the individual securities and the relationships between those securities. Until recently there was no comprehensive theoretical framework for the analysis of the latter aspect of the portfolio problem. Intuitive judgment and experience were the guidelines used by investment managers.