A GLORIOUS, often ghastly, show of paintings goes on view today at the Nationaal Galley of Art. ''Painting in Naples From Caravaggio to Giordano'' is an exhibit that astounds. Its pictures are tremendous -- in both senses of the word.

Not only are they huge, in bravura, in size. To see them is to tremble.

Much sacred Italian art radiates sweet Christian peace, but not the paintings here. Their dismemberments and martyrdoms would make a strong man blanch. Soldiers flog the Savior, arrows pierce the innocent, sharp swords saw at saintly necks, blood soaks into silks. Heads literally roll.

The holy gore that it exudes is not the only reason for this exhibition's impact. Though a number of its pictures sprawl, its scholarship does not. Its argument is focused--one century, one city. Its gory-gorgeous pictures all were made in Naples between the time that Caravaggio, the murderer and master, took refuge there in 1606, and the death of Luca Giordano in 1705.

Seventeenth century Naples, the capital of the Kingdom of the Two Sicilies, was Europe's largest port. Ruled by Spanish viceroys, it was famous for banditti, its volcano, its churches and its slums.

The diarist John Evelyn, in 1645, called it "most magnificent." Its citizens, he wrote, "greatly affect the Spanish gravity in their habit; delight in good horses; the streets are full of gallants on horseback, in coaches and sedans . . . The women are well featured but excessively libidinous. The country people so jovial and addicted to music that the very husbandmen almost universally play on the guitar . . . " The city that he visited was thrice the size of Rome and many times more violent. Seventeenth-century Naples was savaged by catastrophes--earthquakes, revolts, famines, volcanic eruptions and the terrible Black Death, which at its height in the summer of 1656 killed 10,000 to 15,000 inhabitants a day. Corpses black with boils rotted in the streets. We see them in this show. When the pestilence began, Naples was a city of 450,000: 250,000 perished in the plague. The city's suffering and grandeur is apparent in its art.

Given its disasters--and Spain's grave fascination with violence and blood--perhaps it is no wonder so many of these pictures seethe with piety and pain. Their bombast is in some ways less surprising than their freshness. The Naples exhibition is an act of restoration. It rescues from obscurity masters long neglected. These are paintings of a sort that Washington's museums have never shown before.

The finest of these paintings--the Caracciolos, Riberas and graceful Cavallinos--bear far-from-famous names. Caravaggio's, of course, are the chief exception. He was far too influential to be overlooked. He introduced the look of life to high Italian art. Refusing to idealize, he painted from live models. Rejecting heaven's holy light, he peered into the dark. His extraordinary pictures--with their noble shadowed figures lit as if by lightning--changed the art of Italy as quickly and completely as the Impressionists would later change the art of France. He dominates this show.

It is full of ambitious, intelligent painting, none of it well known. The collectors whose art is in Washington's museums snubbed the whole baroque. They gladly spent their millions on Florentine nativities and sweet Raphael madonnas, but martyrdoms upset them. Their tastes were high Victorian, they liked their pictures pure. Andrew Mellon, for example--who would not purchase nudes, much less crucifixions--had no interest whatsoever in Seicento baroque painting.

Not one of the painters in this grand Old Master exhibition is represented in the permanent collection of the National Gallery of Art.

Cool art is out of fashion. The rough, the raw, is in. That may partially explain the increasing ease with which we now accept the art of the baroque. It may be that the tube, or photographs of war, or decades of horror movies, have managed to inure us to its terribilita . At any rate, the timing of the Naples exhibition seems absolutely right.

It is not the sort of show one absorbs at a glance. Its pictures are too big and rich, its names too unfamiliar, its cross-references too twisty. It is best to see it more than once, quickly first, then slowly, then more slowly still. There are many different paths through this enormous show.

One is Caravaggio's. The exhibition opens with his "Seven Acts of Mercy," a huge and complex picture with life-size, life-like figures and strong, dramatic lighting. The flogged Christ in the master's "Flagellation" is a human, not a god; the torturers are bestial, the body bows with pain. Caravaggio overthrew the style--intentionally unreal, mannerist, affected--that had ruled the art of Naples before he arrived. In the next hundred years, many local painters, from Caracciolo to Mattia Preti, would follow his example. His inventions connect scores of paintings in the Naples show.

One way to explore it is as a sociologist, drawing from its images some sense of the violence of that dreadful time. The painters of the city were hard and ruthless men. They viciously competed for the costliest commissions. "When Guido Reni came in 1621," writes scholar Harold Acton in his entertaining preface to the catalogue, "his assistant was so badly wounded that he huried back to Rome . . . Domenichino was then invited . . . This highly sensitive artist accepted the challenge with misgiving, and soon after his arrival he received a letter threatening his life unless he withdrew . . . When the first of his frescoes was uncovered a year later he was so harassed by his local rivals, led by Ribera, that 'he rode day and night almost without rest . . .' It took him another year to decide to finish the frescoes in Naples . . . Poor Domenichino was reduced to such a state of nerves, as Passeri wrote, that his meals became a torment for fear of poison, and his nights for fear of the dagger. And when he died in Naples in 1641, his widow was convinced that he had indeed been poisoned. Annibale Carracci was also reputed to have died as an indirect result of the cabal's harassment . . .

"Ribera behaved despotically to his Neopolitan rivals. When Massimo Stanzione painted a dead Christ for the entrance to the Certosa di San Martino which won general admiration, Ribera persuaded the monks to let him clean it under the pretext that it was too dark. In doing so he ruined it with a corrosive liquid." One need not study martyrdoms, or the corpses strewn about the lower third of Luca Giordano's immense and Goyaesque "Saint Gennaro Frees Naples from the Plague," to shudder at the constant undertone of violence that, from start to finish, rumbles through this show.

Of these 115 paintings, it is hard to pick the most impressive. Here are half a dozen: Caravaggio's "Flagellation"; Caracciolo's crowded, unforgettable painting of a praying soul ascending into Heaven; Artemisia Gentileschi's "Judith and Holofernes"--a harshly gruesome study in feminine revenge by one of the most gifted women painters in the pre-19th-century history of European art; Bernardo Cavallino's treatment of the same theme, in which the executioner, dumbstruck by her act, gazes out, as if in shock, above her victim's severed head; Ribera's awesome "St. Jerome and the Angel of the Judgment," a painting without flaw; Mattia Preti's monumental "St. Sebastian" suffering, in ecstasy, his martyrdom from arrows. One finds in this show's vastness small, delicious passages of nearly perfect painting: the colors and the grouping and the face seen through the veil at the left of Cavallino's elegant and lyrical "The Finding of Moses"; the raised and sunlit hands of Ribera's "St. Jerome"; the pebbles in the pool of Paolo Porpora's "Still Life with Roses, Partridges, Frogs, Owl and a Flamingo" (it isn't a flamingo; it is a black-winged stilt); the haunting head of the "Girl with a Rose" by the Master of the Annunciation to the Shepherds; the long amazing paint-stroke by Luca Giordano that adds sunlight to the cap of the beggar taking alms.

Recent 17th-century gallery exhibits, by accident or plan, have prepared us for this exhibition. "Gods, Saints and Heroes: Dutch Painting in the Age of Rembrandt," the Mauritshaus show, El Greco and Claude all included paintings made at the same time. And the Raphael exhibit, currently on view, partially explains why the baroque art of southern Italy has been so long excluded from the permanent collection.

By the standards of the $8 million Vatican exhibit, this one was a bargain. The Banca Nazionale del Lavoro and Fiat, who each put up less than $200,000, paid for the Naples show.

The gallery's exhibit, which closes May 1, is a slightly smaller version of one seen last year in London at the Royal Academy. Naples' Raffaello Causa, who pried these pictures loose from his city, is most responsible for bringing it about. Clovis Whitfield supervised the London showing. Credit for its well-edited, well-installed Washington display goes to a National Gallery team consisting of curator Sheldon Grossman, Gil Ravenal, Mark Leithauser and director J. Carter Brown.