NEW YORK (AP) _ Bell & Howell Co. common stock surged today after Macmillan Inc. disclosed it had purchased the equivalent of a 6.6 percent stake in the publishing and information services concern and may seek control.

After a delayed opening on the New York Stock Exchange, Bell & Howell was up $10.62 1/2 a share at $69.87 1/2 by midday. Macmillan was up $1.50 a share at $68.50.

In a filing Thursday with the Securities and Exchange Commission, Macmillan said it holds the equivalent of 625,500 Bell & Howell common shares.

It said it purchased 207,700 common shares between July 17 and Tuesday for $56.50 to $61.13 each and bought 2,800 preferred shares from July 13 to July 15 at $55.57 and $55.82.

In the filing, Macmillan said it acquired the shares for investment purposes.

But it also said it intended to monitor future developments in Bell & Howell and might consider seeking control ''by merger, tender offer or otherwise,'' or ''entering into arrangement with third parties who may be interested in acquiring control.''

Macmillan also said it might consider other courses of action, including recommending recapitalization or restructuring plans and seeking representation on Bell & Howell's board.

Bell & Howell, based in Skokie, Ill., had net income of $32.9 million, or $3.10 a share, on sales of $853.4 million in 1986.

It publishes textbooks, prerecorded videocassettes and databases, such as newspapers and catalogues. It also makes equipment to process mail and other documents and to store or retrieve information.

The company, which had once made movie cameras and equipment, has been out of that business for some time.

It has the equivalent of 10.6 million shares outstanding, which values the company at Friday's midafternoon stock price at about $740 million.

Macmillan, which is also involved in publishing, reported a profit of $59.5 million on sales of $818 million in 1986.

It publishes educational and general-interest materials, offers information services and operates the Berlitz Language Centers and several technical schools. It also publishes encyclopedias.