When it comes to spotting the next big takeover, all eyes are on DuPont. It's no secret that the chemical giant wants to expand its life-sciences unit through an acquisition. On May 19, DuPont agreed to pay $2.6 billion for Merck's 50% stake in a joint venture the two companies formed in 1991 to research drugs against AIDS, cancer, and heart disease. The talk on the Street is that DuPont will go after Monsanto or Britain's Zeneca. But some investors are betting DuPont's target is Amgen (AMGN), the world's top independent biotech company.

''DuPont has looked into Amgen's books and operations,'' says one big investor. ''Some investment bankers associated with DuPont have talked informally with Amgen top executives about the prospects of a buyout,'' says another money manager. The word, he says, is that DuPont will make a cash offer for Amgen of $95 a share--for a total of $25 billion. Amgen stock now trades at 61 13/16, for a market capitalization of just over $15 billion. Based on a 1999 earnings estimate of $3.40 a share, Amgen has a price-earnings ratio of 18--or 20, if 1998 earnings of $3.04 are taken as the base.

DuPont CEO Charles Holliday Jr. has said that life sciences will be the cornerstone of DuPont's future. Holliday expects drugs and biotechnology to account for about 33% of earnings in five years, up from 18% today. Amgen has ''a premier position in biotech, and its aggressive R&D spending augurs well for the long term,'' says Herman Saftlas of Standard & Poor's.