Today’s public hearing on the largest development project in Brooklyn’s history is expected to attract large numbers of friends and foes of developer Forest City Ratner’s $4.2 billion Atlantic Yards plan.

The project would include a basketball arena and 16 towers containing more than 2,300 market rate condominiums, 4,500 rental apartments, and office and retail space on 22 acres. Some of the development would be built over the Vanderbilt rail yards, and some on land condemned using eminent domain.

Opponents are worried about the negative effects on the surrounding low-rise neighborhood, while advocates, who include Mayor Bloomberg and Governor Pataki, tout the creation of jobs and much-needed housing.

Some expect today’s hearing, which begins at 4:30 p.m., to run until the auditorium at the New York City Technical College closes — at about 11:30 p.m. Each speaker will be allotted three minutes.

The hearing will proceed despite calls for delay from several elected officials, including the speaker of the City Council, Christine Quinn, gubernatorial candidate Eliot Spitzer, and local council members, as well as civic groups and neighborhood critics of the plan. Some have argued that there was not enough time to sift through a mountain of technical material regarding the development plan, and that mid-August is bad timing because many would-be participants are on vacation.

The state agency overseeing the development, the Empire State Development Corporation, released the draft environmental impact statement and general project plan on July 18 and scheduled the public hearing for six weeks later. They also scheduled a community forum about the project for September 12.

Last week, Mr. Bloomberg said that calls to postpone the public hearing were barely disguised attempts to kill the project. He has supported the project based on the jobs and affordable housing he says it will provide.

“This is a project that has had its exposure to everybody so many times. There’s nothing else you can possibly learn,” Mr. Bloomberg said.

The mayor will not testify today, but his spokesman said the city would submit written testimony before the state closes the public comment period on September 22.The city and state have each agreed to provide $100 million for the project.

A coalition of local community groups, the Council of Brooklyn Neighborhoods, hired independent engineering consultants to review and publish comments on the draft environmental impact statement. They are sponsoring community forums to educate residents how to best respond to the technical aspects of the draft environmental impact statement.

A spokesman for the organization, James Vogel, said volunteers would be outside today’s hearing to help with the expected crowds.

“The public has to do its job, get in there, take a look at the analysis, and make sure it makes sense to the people who know the neighborhood the best,” Mr. Vogel said.

A spokesman for Develop Don’t Destroy, an umbrella organization of groups that oppose the Atlantic Yards, said the strategy to halt the project relies on the courts more than the state’s approval process. The spokesman, Daniel Goldstein, said the group would mount a legal challenge to any condemnation of private property necessary to complete the project.

The ESDC will review public comments received over the next 30 days and incorporate any changes into a general project plan, which requires approval by the agency’s board. The final plan must be approved by the Public Authorities Control Board. The plans say the arena would be completed by 2009 and the project fully built out in 2016.