This is a classic book, representing the first major breakthrough in the field of modern financial theory. In effect, it created the mathematics of portfolio selection in a model which has turned out to be the indispensable building block from which the theory of the demand for risky securities is constructed. "Modern portfolio theory gives a rigorous mathematical justification for the time honored investment maxim that diversification is a sensible strategy for individuals who wish to reduce their risks. Invented in the 1950s by Harry Markowitz in this book, the theory provides a firm foundation for the intuition that you should not put all your eggs in one basket and shows investors how to combine securities to minimize risk." Butron G Malkiel, author of "A Random Walk Down Wall Street" "In every field of study it is possible to look back and identify a person or event that caused a major change in the direction or development of the field. In investments it is clear that the seminal work by Harry Markowitz on portfolio theory changed the field more than any other single event." Frank K. Reilly, University of Notre Dame, Indiana This is a classic book, representing the first major breakthrough in the field of modern financial theory. In effect, it created the mathematics of portfolio selection in a model which has turned out to be the indispensable building block from which the theory of the demand for risky securities is constructed. It also became an essential reference for individuals and financial institutions actually selecting optimal portfolios. Long out of print and unavailable to numerous recent entrants to both financial theory and financial practice, this new edition leaves the existing text as it stands but adds substantial new material including a new bibliography and a fascinating biographical piece on the birth of the field of finance. This is a classic book, representing the first major breakthrough in the field of modern financial theory. In effect, it created the mathematics of portfolio selection in a model which has turned out to be the indispensable building block from which the theory of the demand for risky securities is constructed. It also became an essential reference for individuals and financial institutions actually selecting optimal portfolios. Long out of print and unavailable to numerous recent entrants to both financial theory and financial practice, this new edition leaves the existing text as it stands but adds substantial new material including a new bibliography and a fascinating biographical piece on the birth of the field of finance. Professor Markowitz has been awarded the Nobel Prize for Economics 1990.