NEW YORK (AP) - Health care data company IMS Health and Quintiles, which helps drug companies with clinical trial research, say they are merging in an all-stock deal worth nearly $9 billion.

The combined company will be called Quintiles IMS Holdings Inc. and will have a market value of nearly $18 billion, based on the companies' stock prices Monday.

The new company will keep two headquarters, one at Danbury, Connecticut, where IMS Health is based, and another in Durham, North Carolina, where Quintiles has its offices.