The Dow Jones Industrial Average is comprised of 30 of the largest and most recognizable public companies listed on U.S. exchanges. Examples of these companies include Apple, Goldman Sachs, Visa and Walt Disney. The SPDR ETF (DIA) is one of the most traded ETFs in the world and is comprised of the thirty companies that make up the DOW 30. There is also a full range of short and leveraged Dow 30 ETFs issued by ProShares.