"Montenegro" is either a pornographer's idea of a romance or a romantic's idea of pornography. In this Swedish-Yugoslav co-production, a love-starved middle-aged American housewife, transplanted to Stockholm, stumbles upon her nemesis, a nightclub owner/m.c. originally from Yugoslavia.

She disappears in his club; her initially worried husband, a traveling salesman of Swedish ballbearing swivels (get the symbolism?) receives his share of extramarital excitement too. But in the end her innocent Serbian lover is slaughtered (just as he had earlier slaughtered a lamb for the nightclub -- another ham-handed symbol).

The conflict is not just between convention and passion but between the industrial north and the elemental south, between superior but oh-so-cold Swedish steel and spicy hot Serbian meat.

Action alternates between an immaculate Stockholm mansion overlooking a bay and the Zanzi Bar, a combination nightclub, farm, distillery and junkyard. Yugoslav writer and director Dusan Makavejev gets in a lot of verbal and visual digs at the Swedes. As he tells us in the press kit, originally he wanted to dedicate his film to "the new invisible nation of Europe . . . 11 million immigrants and guest workers who moved north to exploit rich and prosperous people, bringing with them filthy habits, bad manners, and the smell of garlic."

Makavejev succeeds in relieving the boredom of high Swedish respectability with an excursion into Serbian smuggling, violence, singing and, of course, sex.Between displays of genitalia there is much fine acting and good directing. As housewife Susan Anspach, Marilyn Jordan is totally convincing at every station of her round trip between sanity and insanity.

Grandpa Buffalo Bill (John Zacharias) is a perfect cameo of a pistol-wielding crazy old man in a wheelchair who advertises for a new wife and arranges for the candidates to dance for him. He is as solidly real as his two grandchildren, the daughter being a stand- in for mother, the son following the paternal tradition of administrative responsibility. For comic relief -- or is it authenticity? -- there are the denizens of Zanzi Bar.

"Montenegro" is a well-made film whose director's avowed model was "Casablanca" (white house/black mountain). The sex is kinky and more obligatory than apropos; my favorite scene takes place on a bed of loose corn as a nervous white hen watches. But the subtlety of the hero seeing the nude heroine through produce boxes escaped me.

One looking for socially redeeming moments will be suitably aroused by a long scene in which unthinking (and unfeeling) Swedish customs officials search the body of one woman and the baggage of another. Their insistence on confiscating and destroying what seems to be a roasted boar and bottles of plum brandy (or maybe it was olive oil) brought in from Yugoslavia may prompt gourmets to boycott smorgasbord.

In terms of sexual encounters Yugoslavia scores two to one against Sweden. But it's "Casablanca" six, "Montenegro" one. MONTENEGRO -- At the Key.