Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of medical research company Covance (UNKNOWN:CVD.DL) have leapt more than 25% Monday after agreeing to be acquired by Laboratory Corp. of America (NYSE:LH) for $6.1 billion in cash and stock.

So what: LabCorp will pay $105.12 for each Covance share -- a 4.9 % premium over the stock's current price of roughly $100.25 -- with $75.76 of the purchase price paid in cash and the balance paid in LabCorp shares, which would make Covance shareholders owners of approximately 16% of LabCorp, according to news reports. The deal includes LabCorp's assumption of roughly $500 million in Covance debt, and each Covance share will be converted into 0.2686 LabCorp shares after the cash payment.

Now what: Prior to the deal, LabCorp and Covance shares had produced almost exactly the same return over the past five years, with Covance gaining 51.2% to LabCorp's gain of 56%. Both results trail the S&P's near-doubling over the same time frame, and LabCorp's 8% drop on the deal indicates that its current shareholders aren't too keen on the tie-up. If you were waiting for a good time to get out of Covance, you've got it today.

Alex Planes has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not 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.