In what is being billed as the largest mass conversion in history, up to one million lower-caste Hindus or dalits are expected to convert to Buddhism in India next Sunday.
Leaders of the dalits, formerly known as "untouchables", say the change of religion will free them from the scourge of the discriminatory caste system and the abuses they suffer on a daily basis.
The proposed mass conversion has received the approval of the Dalai Lama, the head of Tibetan Buddhism, as well as of leading Christian organisations. The ceremony is due to be held in New Delhi.
"Caste is our main problem", says a dalit leader, Mr Ram Raj, who will be among those converted. "It pervades all aspects of life in India, though it is not always visible. This is our way of escaping the misery of living on the margins of society."
Next Sunday's ceremony was originally due to have been held some weeks ago, on the 45th anniversary of the first mass conversion of Hindus. On that occasion, more than 300,000 lower-caste Hindus embraced Buddhism. They were led by B.R. Ambedkar, the man who framed the Indian constitution.
"He is our messiah, a godly figure for the dalits," says Mr Ram Raj. "In converting to Buddhism, we will be emulating him.
"Our choice of religion is also dictated by the fact that in olden times, much of India was Buddhist. This deeksha (conversion) will be like returning to an old house and it will liberate us from bondage."
Some 200 million people - a fifth of India's one billion population - belong to the lowest part of the caste system.
Officially grouped under the term "scheduled castes", the dalits or "broken people" are so low in the Hindu hierarchy they exist outside the framework of caste.
"Christian groups, as well as Muslims and Sikhs, plan to attend the ceremony," says the Rev John Dayal of the All Indian Christian Council which represents non-episcopal churches in India.
"We want to show solidarity with the dalits. If any of them want to come over to Christianity - and I pray they do - then we will welcome them. With us they will find open doors and open hearts."
The Dalai Lama has said the move to Buddhism will be a step towards equality in Indian society for the dalits. Their decision to convert should not cause resentment among other religions or castes, as Buddhism and Hinduism were, as he put it, like twins.
Mr Dayal has speculated that conversion to Christianity might be a more pointed rejection of caste Hinduism. Buddhism, which was founded in northern India in about 500 BC, enjoys close cultural links with Hinduism.
However, Hinduism is alone in having a hierarchical caste system.
At its root is the notion of karma, according to which people are what they are because of what they were and what they did in past lives.
Discrimination by caste is outlawed in India but remains part of life for millions of people, particularly in rural areas. Such tasks as raising pigs, cremating the dead and cleaning latrines are traditionally reserved for dalits.
In many villages, they cannot drink from the same cups or even the same wells. Even primary school children are divided in the classroom according to caste.
The government has passed a package of legislation to increase the dalits' work and social opportunities, including set quotas for dalits in political bodies, government jobs and education.
But critics say discrimination is so pervasive that it continues to hamper the social advancement of dalits.
"Bad postings and lack of promotion is bad enough," says Mr Ram Raj, a senior civil servant in the Indian Finance Ministry." But rape, beatings and murder are the lot of many dalits throughout India."
It is expected that some hardline Hindu organisations may try to disrupt next Sunday's conversion ceremony.
High-caste landlords frequently employ armed gangs of thugs to set upon dalits who rebel against their status as cheap or bonded labourers.
"If there is intimidation, then we will have no choice but to hit back," says Mr Ram Raj.
"But I hope there'll be no conflict. This conversion is a form of protest, but it is also meant to be a peaceful occasion."