Many websites provide information on which companies are included as components of different stock indexes. Knowing what indexes a company's stock is in can be an important part of predicting future movement. News that affects markets and sectors as a whole may move all of the stocks within the index, regardless of whether the news is directly about the company.

One place to find lists of index components or company stocks that make up an index is the website of the index maker. For example, you can find the list of company stocks included in the Nasdaq 100 by going to

Going straight to the primary source—the website of the index maker—is usually ideal. However, this list isn't always available or easy to find on the website for every popular index. Often, it's easier to go to a website like Yahoo Finance or MarketWatch that aggregates this information so you can find it in one place.

Notable Stock Indexes

There are many stock indexes available, but the following are some of the major ones:

There are several ETFs and mutual funds that are designed to track the major indexes, such as the SPDR Dow Jones Industrial Average ETF (DIA), which tracks the Dow, and the PowerShares QQQ ETF (QQQ), which tracks the Nasdaq 100.

Where Else to Look

Yahoo Finance: First, head to the Yahoo Finance quote page. Next, you can either type in the name or symbol of an index into the quote box, such as the Dow Jones Industrial Average, or click one of the shortcut links in the bar at the top of the page.

Once you're viewing the summary page of the selected index, click the link to "Components." That's where you'll find the list of stocks that are included in the particular index you are researching.

MarketWatch: If you go to the MarketWatch home page, you'll see a list of some of the most notable industry indexes. If you click on one, such as the S&P 500, you'll come to the overview page for that index. If you scroll down a bit, you'll see a list of the companies that are included in the index divided into top performers and bottom performers.

The component stocks of indexes can change frequently. Getting the list of companies on an index directly from the index maker is always the ideal option for making sure you have the most up-to-date information.