Box Office Information (as obtained by Wikipedia):
Sholay was released on 15 August 1975 in Mumbai. On 11 October 1975, the film was released in several other Indian film distribution districts. It earned Rs. 1,62,41,00,000 equivalent to US$ 88 million, after adjusting for inflation and remains the highest grossing movie of all-time in the history of Indian Cinema.
At Mumbai's Minerva theater, it was shown in regular shows for three continuous years, and then in matinee shows for two more years. Even in 240th week of its release, Sholay was packing the theaters. Sholay grossed about 35 crore rupees in its first run, a record that remained unbroken for the next nineteen years. Sholay ran for more than five years.