Marion Laboratories was the Big Board's busiest issue on a volume of more than 1.74 million shares.

Marion Laboratories rose 1 1/8, to 73 3/8, after the company presented a bullish earnings assessment at a meeting of securities analysts.

Also in the drug group, Richard R. Stover again chooses Marion Laboratories as his favorite.

Marion Laboratories rose 1/2, to 35 3/4, on news that one of its important drugs would have annual sales of about $600 million.

Marion Laboratories, the most-active issue on the Big Board, with volume of 5.7 million shares, was down 1/2, to 34 1/2.

Dow issued the rights in December 1989 as a deferred payment when its pharmaceutical unit merged with 67 percent of Marion Laboratories.

At the time Marion Laboratories was outperforming all other drug company stocks by 2 times.

In 1964 it formally incorporated at Marion Laboratories, Inc.

Mr. Frank, 57, has put together several big transactions in the health care field, including the marriage of Marion Laboratories with Merrill Dow.

Analysts are also troubled by Dow's acquisition of a 67 percent stake in Marion Laboratories last year.