WASHINGTON -- When congressional staffers check the office inboxes each morning, they've got mail -- sometimes hundreds of pieces of it.

A new report released by the Congressional Management Foundation, a nonpartisan congressional watchdog, found that members of Congress were flooded with more than 200 million pieces of correspondence in 2004, four times the 50 million in 1995.

The report, which is based on a survey of 202 House and Senate offices, said 91 percent of the messages, or 182 million, were sent online, while only 9 percent, or 18 million, were sent by U.S. mail.

In 1995, most of the 50 million messages were sent via postal mail, a method that has fallen out of favor ever since a strict inspection process was implemented after anthrax was discovered in letters sent to Capitol Hill shortly after the Sept. 11 terrorist attacks. Today, it can take weeks for mail to get through.

"Without a doubt, there's been a huge spike in correspondence from our constituents, most notably via email," said Paul Callahan, legislative correspondent for Rep. Joe Wilson, R-S.C. "It usually means spending a lot more early mornings and late nights for me."

Most online communication arrives via Wilson's Web site's online form, a tactic many lawmakers have turned to in an attempt to streamline the communications process.

Callahan estimates that he receives and processes about 500 emails a week -- mostly focusing on hot-button issues, such as Social Security, CAFTA and stem-cell research. His office replies to 95 percent of them.

Many times, he said, the return correspondence is in the form of a "canned response" tailored to the subject of the message -- especially if the letter focuses on an ongoing issue.

Even so, Callahan said, all messages are considered carefully.

The report highlights the importance of correspondence between constituents and their representatives. For example, 79 percent of those surveyed believe the Internet has made it easier for a citizen to get involved in the public policy process.

Wesley Denton, communications director for Sen. Jim DeMint, R-S.C., said his office receives between 1,000 and 3,000 emails a month from constituents.

DeMint's office recently revamped its Web site, adding an extended topic list that allows letter writers to have their messages directed to the people in the senator's office assigned to handle their issue of interest.

"It's one of the fastest ways for people to communicate their issues to the senator," Denton said.