DEERFIELD, Ill. » Drugstore chain Walgreen Co. said Friday that Chairman and CEO Jeffrey Rein has retired from the company after 26 years.

Rein, 56, will be replaced as company chairman by Alan McNally, 62, lead director on Walgreen's board. McNally will also serve as acting CEO while the board searches for a permanent replacement. The company specified no reason for Rein's departure. He had been CEO since April 2006.

Some analysts speculated Rein may be leaving because of differences with the board of the company.

“;Given's Mr. Rein's age (56) and relatively short tenure, we wouldn't guess this to have been voluntary on his part,”; SunTrust Robinson Humphrey analyst David Magee said in a note to clients.

Magee said Rein made some good decisions, including getting the company into the specialty pharmacy business and paring back store growth. But he said Walgreen's sales were soft in the past few quarters, and “;outsiders”; were unhappy with the way Walgreen went after Walnut Creek, Calif.-based Longs Drug Stores, which has 41 locations in Hawaii, including two under construction.

Walgreen, which entered the Hawaii market last year to compete with Longs, said last month it is negotiating what would be its eighth location in the state.