Father Mustos was born in Veszprém, Hungary. He studied at the Piarist Fathers school of his native town, and joined the Piarist order in 1949.

Because of oppression of religions in Communist Hungary, he had to interrupt his studies for the priesthood to work in a chemical factory, and then he served in the army. From 1954 until 1956, he taught at the Piarist school in Budapest.

After the failed Hungarian revolution of 1956, Father Mustos left the country and studied theology at Pontifical Gregorian University in Rome, where he was ordained in 1958.

The next year he came to the United States and earned a master's degree in mathematics and physics at Canisius College in Buffalo in 1966. He taught at the Calasanctius School in Buffalo from 1960 to 1969.

From 1969 to 1987, Father Mustos was headmaster of Devon Preparatory School, where he also taught math and Latin.

In 1970, he celebrated the school's first Christmas midnight Mass, now a tradition. The next year, he instituted the school's first open house and started the Advanced Placement program there.

In 1972, he added seventh and eighth grades to Devon Prep's four-year program. He supervised the construction of an athletic field in 1975.

In 1985, he became president of the Association of Hungarian Priests on the East Coast of the United States. From 1987 to 1990, Father Mustos was chaplain of St. Stephen's Church in Trenton. He moved to Passaic, N.J., in 1990 to become pastor of St. Stephen's Magyar Church there.

One of Father Mustos' real joys was his work among Hungarian immigrants, said Jose Burgues, secretary provincial of the Piarist Order.

From 1989 to 2006, he was the American delegate to Bishop Attila Miklósházy, the bishop of Hungarian Roman Catholics living outside of Hungary.

Even from Passaic, Father Mustos made the trip to Devon to celebrate a Hungarian Mass once in a month, said Ákos Felsövályi, member of St. Stephen's Magyar Church in Passaic.

Father Mustos held retreats all over the Eastern United States and Canada, Felsövályi said.

Father Mustos retired from active ministry in 2007, and for the last 10 months he resided at a nursing home for priests in Székesfehérvár, Hungary.

He is survived by a niece.

A Funeral Mass will be said Wednesday at the Chapel of the Piarist Fathers in Budapest. Burial will be in Rákoskeresztúri Cemetery, Budapest.

Memorial donations may be made to Piarist Fathers Seminarian and Retirement Fund, 4605 Bayview Dr., Fort Lauderdale, Fla. 33308.