During fiscal 1997 the top 100 city contracts accounted for a whopping 50 percent of all city contracts and the top two winners were other city agencies, according to the latest edition of City Law, put out by New York Law School.

A full $2.9 billion of the total contract value of $5.8 billion went to the top 100, up from last year's figure of $2.6 billion, or 42.2 percent of the total value.

The biggest city contracts were given to its own agencies. The Department of Health paid the Health and Hospitals Corporation $227 million to provide health services to people in prison, communities and children until 1998. And the Department of Citywide Administration tapped NY Power Authority, to install cost-efficient technology across the city over the next 17 years for $150 million.

Other big spenders were the Department of Environmental Protection and the Department of Transportation. DEP spent its $719 million through 22 different contracts on watershed protection and sewage treatment cost, including $30 million to Putnam County for watershed administration. And the reconstruction of the Williamsburg and Manhattan bridges cost the DOT $284 million awarded in four mega contracts, including a $129 million contract to Koch/Nad Joint Venture and another $124 million to Yonkers Contracting Co.

Another eight contracts, valued at $118.4 million, went toward the rehabilitation of in rem buildings taken over by the city. And Volunteers of America won $69 million from the Department of Homeless Services for running homeless shelters for men.

For four consecutive years, the city has spent a diminishing amount on contracts. City contracting took a $400 million hit in fiscal year 1997, 6.5 percent less than the year before. For a copy of the list, contact City Law at 212-431-3295.