From January 2000 through June 2005, lawmakers and their aides took at least 23,000 privately funded trips with a total value of almost $50 million.
Almost three-quarters of the trips were taken by staffers, who often influence how their bosses view issues and vote.
Ethics rules require that such trips be educational or investigative, but many were to vacation destinations — at least 200 to Paris, 150 to Hawaii and 140 to Italy.
Of the two dozen congressional offices on which trip sponsors spent the most money, 15 were Republican.
Of the 25 lawmakers who each accepted more than $120,000 worth of travel for themselves, 17 were Democrats.
At least 11 offices accepted more than $350,000 each in travel. Top beneficiaries included the offices of Reps. Tom DeLay, R-Texas, and Don Young, R-Alaska.
Ethics rules infractions involving travel usually go unpunished.