Mr. Spitzer's office will join a lawsuit challenging the county's assessment system on the grounds that it discriminates against black and Hispanic homeowners, officials said today.

Black, white and Hispanic homeowners with comparable credit scores will make loan applications to see if borrowers are treated equally.

The study showed that about 40 percent of black and Hispanic homeowners have F.H.A. loans, while only 17 percent of white owners do.

Black homeowners are more likely than Hispanic and white homeowners to experience severe and moderate housing problems.

A far greater share of black and Hispanic homeowners with above-average incomes still have mortgages with higher interest rates than whites with comparable incomes, according to a study to be released today.

From 2005 to 2009 Hispanic homeowners' home equity declined by Half, from $99,983 to $49,145, with homeownership rate decreasing by 4% to 47%.

The Justice Department says Nassau County's method of assessing property taxes discriminates against black and Hispanic homeowners, causing them to pay disproportionately high taxes, according to Government documents.

Many residential blocks are a mix of black, white and Hispanic homeowners.

A federal civil rights lawsuit charging that Nassau County's antiquated tax assessment system discriminates against black and Hispanic homeowners was thrown out of federal court here today.

"It's a strange block," Ms. Bick said as she stood at the window of her loft, a neighborhood cookout given by Hispanic homeowners just barely visible below her.