I am still indebted to Nathan Mitchell, a colleague at the University of Notre Dame and a liturgical scholar of the first rank, for most of the historical details in this week's column, as I was in the original version five years ago. (See his "Holy Week" in The HarperCollins Encyclopedia of Catholicism, pp. 636-37.)

Holy Week, as everyone knows, is observed during the final week of Lent, with its liturgical climax at the Easter Vigil and then on Easter morning itself.

It reenacts the main events of Jesus' last days: his entry into Jerusalem (Palm Sunday), the Last Supper (Holy Thursday), his arrest and trial, the carrying of the cross, and the Crucifixion itself (Good Friday).

The early Christians, however, were content each year to recall Christ's suffering, death, and Resurrection in a single, unified liturgical celebration known as Pascha (Greek for the Christian "Passover," or Easter). This yearly paschal observance occurred either on a fixed day of the lunar month, which would have been according to the Jewish tradition, or on the Sunday that followed it.

After much internal struggle over the issue, the ancient Jewish date was eventually set aside, and it was determined that the Christian "Passover" (Easter) would always fall on Sunday, which the Christians traditionally regarded as the Lord's Day and as the Church's weekly opportunity to celebrate the triumph of Christ over death in his Resurrection.

A key liturgical development had occurred in the fourth century, however. The earlier, unified celebration of the Christian Passover was now split into a series of liturgies that reenacted in greater detail the events of Jesus' final week of earthly life.

The original venue for this development was in the city of Jerusalem, where numerous shrines had already grown up on the very sites where the holy events were believed to have happened.

Detailed descriptions of the Holy Week liturgies conducted in Jerusalem at the time were provided in a travel diary kept by a European woman whose name, Egeria, is known to all liturgical scholars and their graduate students. She had been part of a pilgrimage to Jerusalem in the year 383.

According to Egeria, the ceremonies for Palm Sunday, Holy Thursday, Good Friday, and Holy Saturday were especially noteworthy.

On Palm Sunday afternoon an elaborate procession began outside Jerusalem at the Mount of Olives, where Jesus was traditionally thought to have ascended into heaven. The bishop reenacted the role of Christ, while children waved palm branches as the procession wound its way through the entire city.

On Holy Thursday night, after the Eucharist had been celebrated in the afternoon, the events of Jesus' agony were reenacted: his prayer in the Garden of Gethsemane, his arrest there, and his appearance before Pilate.

On Good Friday there were four hours of veneration of the cross, beginning before noon, followed by a solemn afternoon Liturgy of the Word that concluded with a reading of the Passion according to John.

The Easter Vigil, which focused on the celebration of Baptism, began in mid-afternoon on Holy Saturday, with the final preparation of adult catechumens. That night, while the catechumens were being baptized, the rest of the faithful kept vigil. When the newly baptized were led into the church, the celebration of the Easter Eucharist began.

According to Professor Nathan Mitchell, this shrine-centered pattern of "representational" services soon caught on everywhere in the then-Christian world, even among communities that had no historical or geographical connection with the sites where the original events were thought to have occurred.

By the fifth and sixth centuries, the highly influential churches of Rome and Constantinople had adopted these Holy Week liturgies. The liturgies subsequently spread from these centers to other local churches within their vast jurisdictions, both in the West and in the East.

Unfortunately, the linkage between the liturgies of Holy Week and the original times and places of the sacred events became obscured in the medieval West. The situation was not remedied until the restoration of Holy Week that was mandated by Pope Pius XII in 1956, and the liturgical reforms of the Second Vatican Council a few years later.

Nowhere were these changes more evident than in the celebration of the Easter Vigil. Prior to the restoration of the Holy Week liturgies, Holy Saturday was the least popular of all of that week's liturgies.

I know whereof I speak. The long and complicated ceremony was conducted entirely in Latin, early on Holy Saturday morning, with only a handful of people and a few unlucky altar boys in attendance.

Looking back now, the restoration of Holy Week remains one of Pope Pius XII's greatest achievements."

Father Richard P. McBrien is the Crowley-O'Brien Professor of Theology at the University of Notre Dame.