One of Washingtons oldest corporations, the printing company of Judd & Detweiler Inc., has won the largest contract in its history from Newsweek magazine.

Starting next year, Judd & Detweiler will begin printing, binding and mailing the entire Middle Atlantic region press run for for the news magazine - about 550,000 copies.

Newsweek, a subsidiary of The Washington Post Co., signed a 10-year contract with Judd & Detweiler valued at about $25 million.

In addition, Newsweek signed a similar contract for production of 550,000 copies to be circulated in New England with City National Printing Co. of Greenwich, Conn.

The two editions involved in the new contracts currently are printed by the R.R. Donnelley & Sons Co. in Old Saybrook, Conn. (since 1974) and Lancaster, Pa. (Since 1975).

A spokesman for Newsweek said yesterday the decision to switch from Donnelley was made because of "a variety of different issues on which we couldn't come to agreement." He described the Washington and Greenwich printers as "the best we could find."

Under the agreements with Newsweek, the printing firms will receive binding and mailing systems from the magazine under a lease. The new equipment will be capable of operating up to 50 percent faster than facilities now used in the magazine industry, Newsweek stated. The transition to new printers will be completed by mid-1979.

Judd & Detweiler, which will celebrate 110 years in business on Nov. 2, is one of the area's largest printers with about 1,000 employes at its main plant in Northeast Washington and subsidiaries in Baltimore and Strasburg, Va., organized under a parent firm, Judd's Inc.

For nearly three-quarters of a century until 1957, Judd / Detweiler printed National Geographic magazine here until circulation topped 2 million and the magazine switched to a Midwest firm with faster presses.

The Washington company prints more than 50 other periodicals, annual reports, maps and other documents. Annual sales are estimated at $17 million.

Currently, Judd & Detweiler prints a portion of Newsweek. A spokesman said yesterday the full Newsweek runs will be produced at the D.C. plant, Eckington Place and Florida Avenue NE, and in Strasburg.