Men are not discriminated against by "ladies' nights" at Manhattan nightclubs, just as people in their 20s do not suffer because some restaurants let children eat for free or have "early bird" specials for older customers, according to nightclub lawyers fighting a federal lawsuit.

Roy Den Hollander has sued clubs including Lotus and the China Club, saying he was discriminated against by ladies' nights, which offer women free or discounted admission and drinks.

Deborah Swindells Donovan, a lawyer for Lotus, called the lawsuit frivolous in papers filed Friday in U.S. District Court.

She wrote that if his "ill-conceived theory is applied to restaurants, then 'early bird' specials for the elderly or promotions allowing children to eat free would be discriminatory on the basis of age."

Vanessa R. Elliott, a lawyer representing the club AER Lounge, said in court papers Friday that nightclubs recognize that men might not want to visit the clubs if they fail to attract enough women.

"Under this theory, male customers may actually benefit from ladies' nights in other ways and be encouraged to attend the club on those nights," she wrote.

The price charged to men is not so burdensome that it amounts to denying them entry, Elliott argued.

In his lawsuit, Hollander said he sought to represent all men over age 21 who had entered one of the nightclubs since June 21, 2004, and been subjected to policies that provide discounts to women of the same age.

He asked a judge to conclude that the policies violated the Constitution and to assess minor damages against the clubs.