A Congressional hearing called to examine intellectual-property and trademark issues on the Internet became sidetracked today by questions about who was responsible for a flurry of obscene addresses on the World Wide Web.

The hearing by the Courts and Intellectual Property Subcommittee of the House Judiciary Committee brought together officials from the Commerce Department and Network Solutions, a government contractor in Herndon, Va., that had held a monopoly on registering Internet addresses ending in the domain names .com, .net and .org.

Network Solutions has a policy against objectionable or vulgar names. But this spring, the Commerce Department had authorized five other companies to begin competing in the registration process on a trial basis. And Network Solutions, which continues to administer the system, decided not to impose its rules on the competitors.

That decision had resulted in a rush of domain-name registrations using obscene or vulgar words.

Representative Christopher B. Cannon, a Utah Republican, said the episode had raised concerns about the Commerce Department's ability ''to oversee how this process should go forward and how well it works.''