This is actually a growing controversy in India. Historically, during the Vedic period, polygamy was neither allowed nor prohibited. Currently, under Hindu Marriage Law, as understood by the constitution of India, polygamy is forbidden for Hindu, Jains, and Sikhs. But in India, this law seems largely dependant on the religion of the individual. Muslims in India can have multiple wives as per their religion. There have been attempts to create a uniform law, but so far, it has been unsuccessful.
This probably would not be a problem, were it not for the fact that Hindu's wanting multiple wives have converted to Islam. It was perceived as such a problem in India that they made a law forbiding any Hindu that converted to Islam from taking a second wife. This effectively makes all Hindu polygamy outlawed. (Officially outlawed, anyway. Many remote areas still practice polygamy regardless.)
Hindus regard the institution of marriage as a sacrament and not just a contract between two persons of opposite sex. This Hindu alliance is as much a union of two families as between two individuals. It's a lifelong commitment and is the strongest social bond between a man and a woman.
Note that marriage is sacrosanct, Hindus believe that marriage is not only a means of continuing the family but also a way of repaying one's debt to the ancestors. The Vedas affirm that a person after the completion of his student life should enter the second stage of life, that is, the Grihastha or life of a householder.
According to the scriptures, a Hindu marriage is indissolvable in life. Polygamy was rampantly practised in ancient Hindu society. In an address by Bhishma to King Yudhishthira in the Mahabharata: "A Brahmana can take three wives. A Kshatriya can take two wives. As regards the Vaishya, he should take a wife from only his own order. The children born of these wives should be regarded as equal." (Anusasana Parva, Section XLIV). But now that polygamy has been completely eradicated by law, monogamy is the only {legal} option for Hindus.