"You won't invite them home, you won't go over to their home," he said.

Other upper-caste Indians here say that they do not bother to probe someone's caste and that most compatriots will do business with anyone. Few Indians would admit to such behavior as refusing to eat in a restaurant because its food was cooked by an untouchable.

Mostly caste survives here as a kind of tribal bonding, with Indians finding kindred spirits among people who grew up with the same foods and cultural signals. Just as descendants of the Pilgrims use the Mayflower Society as a social outlet to mingle with people of congenial backgrounds, a few castes have formed societies like the Brahmin Samaj of North America, where meditation and yoga are practiced and caste traditions like vegetarianism and periodic fasting are explained to the young.

"Right now my children are living in a mixed-up society," said Pratima Sharma, president of the New Jersey chapter of Brahmin Samaj and a 39-year-old software trainer with two daughters, 9 and 3. "That's why I went into the Brahmin group, because I wanted to give my children the same values."

The exquisitely complex Indian caste system dates back thousands of years to the origins of Hinduism. Hindus tell of a deity who transformed himself into a human society arranged according to a cooperative division of labor. The deity's head turned into the Brahmin caste of priests and scholars, his hands into the Kshatriya caste of warriors and administrators, his thighs into the merchant and landholding Vaishyas, and his feet into Shudras, the skilled workers and peasants. Hindu notions of ritual purity and pollution defined how these four broad castes could interact and reserved an underclass rung for the untouchables, who worked in the most "polluting" jobs, such as cleaning streets or toilets.

Whatever its economic and religious foundations, the caste system - which in time sprouted more than 3,000 jati, or subcastes, tinged by geography, language and employment - became ironbound. Until recent decades, village untouchables would step out of view whenever a Brahmin walked by, and tea stalls would reserve separate dishware for Dalit.

After India gained independence from Britain in 1947, the legal forms of caste were abolished, and lower castes began benefiting from favorable quotas for government jobs and college entry. By the mid-1960's, the social aspects of the system were also slackening among urban and educated sectors of Indian society, precisely the groups that furnished most of the doctors, engineers and other professionals who began coming to the United States under preferences in immigration law.

Then something surprising happened here. Madhulika S. Khandelwal, director of the Asian American Center at Queens College, said that the continuing influx of immigrants brought in less-educated relatives who tended to sustain caste distinctions, and created masses of caste members who could associate easily with one another. In the 2000 census, 454,686 Indians were in the New York-New Jersey-Connecticut metropolitan area.