The Wall Street Journal reported on the deal talks Thursday. The newspaper cited people familiar with the matter and said CVS might pay more than $200 a share for the nation's third-largest health insurer, valuing the company at some $66 billion.
Spokesmen for both companies declined to comment on the report.
Aetna's stock jumped $18.46, or 11.5 percent, to close Thursday at $178.60. CVS shares shed nearly 3 percent, or $2.21, to close at $73.31.
CVS Health is the nation's second-largest drugstore chain and also processes more than a billion prescriptions annually as a pharmacy benefits manager. Aetna insures more than 22 million people.
CVS Health is based in Woonsocket, Rhode Island, and Aetna is based in Hartford, Connecticut.