SAN FRANCISCO -- About 77 percent of Mac users in the U.S. are running Microsoft's Office for Mac, the Redmond company said today. That might not rival Office's presence on Windows PCs, but it's notable in part because of Apple's push into word-processing and spreadsheet programs in recent years.

Microsoft disclosed the statistic for the first time here at Macworld Expo, as it marked its 25th anniversary of releasing software for Apple computers. At this point, however, the number is more interesting factoid than meaningful trend. That's because it's a new study and even Microsoft doesn't know exactly what the comparable figure was in the past.

"This has been a more complete piece of research" than Microsoft conducted internally in the past, said Amanda Lefebvre, senior marketing manager in Microsoft's Mac Business Unit.

At the same time, the U.S. focus is a limitation. "We anticipate that it will be proportional worldwide, but we just don't know yet, so we're looking to run more research in additional regions, as well," Lefebvre said.

Also at Macworld today, Microsoft discussed plans for two Mac Office updates aimed at connecting Mac users more smoothly with Microsoft's back-end computer servers.

First, the company said it will be releasing an update for Entourage aimed at letting users of the Microsoft Mac e-mail program connect more smoothly with Microsoft Exchange Server 2007. That free update, called Entourage for Exchange Web Services, will help in areas such as calendar and notes synchronization, the company said. It will be released as a public test this month and in final form later this year, the company said.

In addition, Microsoft said it's developing a new Mac application called the Microsoft Document Collaboration Companion to help Mac users share documents through Microsoft's SharePoint and Office Live Workspace collaboration services. That program is slated for release in final form later this year, as well.

Microsoft released Word 1.0 for the Mac in 1984. Office for Mac now includes Word, PowerPoint, Excel, Entourage and Messenger.

Apple has moved more aggressively into the productivity software market in recent years with the release of the Numbers and Pages programs as part of its iWork suite of applications, which also includes its Keynote presentation software. The company introduced a new version of iWork today, along with a related iWork.com online collaboration service.