The first weekend of late-night service on Metro attracted less than two-thirds the ridership the transit agency had initially projected, but Metro officials said yesterday that they think the figure will increase as more people become aware of the extended hours.

In the first expansion of its evening hours since 1978, Metro extended rail service from midnight to 1 a.m. Friday and Saturday night, the beginning of an eight-month experiment. That extra hour generated 5,260 passengers on the two nights combined, Metro spokesman Ray Feldmann said.

Before the extra service began, Metro officials had said they expected to attract 4,500 additional riders each night, for a weekend total of 9,000.

But Feldmann said yesterday that 9,000 is a ridership target to be reached by June. At that point, Metro directors will assess the popularity of the service, its impact on the transit system and whether it should be continued, expanded to 2 a.m. or cut back to midnight, the closing time on other nights.

"This is an eight-month pilot program, and we don't expect to hit our maximum projection the first weekend out of the box," Feldmann said. "On Friday night, when we were handing out promotional material, people were saying, 'Oh gosh, I forgot that started this weekend.' Once it becomes ingrained in people's minds, we expect those numbers will go up."

Jim Graham, a Metro board member and leading advocate for late-night service, said the initial reception to extended hours was strong but needs to be boosted through increased marketing.

"We're going to have to move Metro into a far more aggressive marketing posture on this and other matters," said Graham, a D.C. Council member whose Ward 1 includes the nightlife magnets of Adams-Morgan and U Street. "If we want Metro to be seen as a late-night option, we have to make an effective effort."

Metro ran newspaper and radio advertisements and hung messages in trains and buses a couple of days before late-night service began. Feldmann said Metro officials decided against earlier marketing because they did not want to confuse the public. "We purposely waited because we didn't want to run advertising the week before and run the risk of having passengers think it was starting that week," he said.

Cleatus E. Barnett, who represents Montgomery County on the Metro board, said it was premature to interpret the figures as either success or failure.

Barnett and at least two other board members have expressed concern that the late-night service will mean less time for subway maintenance. Metro does most of its heavy maintenance work when the system is shut down.

During the additional hour of operation between midnight and 1 a.m. on Friday night, 2,457 passengers entered Metro's 78 rail stations. On Saturday night, 2,803 passengers used the system during the extended hour of operation.

The busiest stations for the late-night service were Dupont Circle, Union Station, Foggy Bottom-GWU and Woodley Park-Zoo.