When insiders buy shares on the open market, their companies could enjoy bullish times ahead. Corporate insiders often have the inside track on their companies' prospects, and many of them get paid largely in stock options or restricted shares. Besides, insiders probably wouldn't risk plowing too much of their own money into their own company's stock -- reducing their portfolio's diversity, and increasing its risk -- unless they thought the stock might rise.

With that in mind, I screened for companies where at least one insider made an open-market buy in the last 30 days. These seven health-care stocks made the list.

Security

Net Number of Buys

No. of Shares Bought

Total Value

Market Cap (Millions)

Opko Health (AMEX: OPK)  1  50,000  $170,000  $1,236
Novavax (Nasdaq: NVAX)  1  50,000  $102,000  $222
Esterline Technologies (NYSE: ESL)  1  1,235  $100,000  $2,366
BioTime (AMEX: BTX)  2  15,400  $68,000  $244
Rockwell Medical Technologies (Nasdaq: RMTI)  1  4,000  $52,000  $220
Covance (NYSE: CVD)  1  800  $46,000  $3,617
Chemed (NYSE: CHE)  1  170  $11,000  $1,374

Source: Capital IQ, a division of Standard & Poor's, as of July 18, 2011.

When it comes to the number and total value of insider open-market buys, more can be better; I've sorted this table accordingly. An insider at Opko Health made an open-market purchase worth a total of $170,000 while a Chemed insider spent only $11,000 on an open-market buy. Both are bullish signs, but the Opko Health purchase looks a lot more promising. What's more, Opko Health is the lone repeat from the 11 stocks that made the list when I ran the screen a month ago.

Foolish takeaway
Insider buying signals that someone who should be in the know is betting that the stock will rise. You can use this list of recent insider purchases as a starting point for further research -- or a good reason to make a contrarian play.

Are these insiders right? To help you find out, The Motley Fool recently introduced a free My Watchlist feature. You can get up-to-date news and analysis by adding these companies to your Watchlist now.

Fool contributor Cindy Johnson currently owns no shares of any stock in this story. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.