Jai alai -- fast, exciting and a challenge to the agile -- has been shunned as a participatory or spectator sport in America during the past 45 years, and instead played primarily for the benefit of gamblers.

The game evolved some 200 years ago in the Basque area of Europe, a mountainous region in Northern Spain near the French border, where players strapped baskets to their hands and used them to catch and throw balls against the walls of buildings.

Today, the game is played on a three-walled court, usually 168 feet long, usually by two two-man teams. The players have long wicker baskets called cestas tied to their hands, and the teams alternate throwing the pelota (a hard rubber ball covered with goatskin) against the front wall.

They execute a variety of tricky carom shots, put devilish spin on the pelota and throw it at speeds up to 180 miles an hour. A team scores a point when the ball bounces on the floor twice or an opposition player drops it.

In the game's primordial form, spectators would bet on every point. But when the game (and a full complement of Basque players) came to Miami in 1935, its structure was changed to accommodate American-style parimutuel wagering.

Each jai alai establishment (called a fronton) hires its own stable of players, most of them Basques and pays their salaries along with some bonuses for winning games. These 40 or so players will compete against each other every night, with the pairings for each game determined by the fronton's matchmaker.

Eight teams participate in each game. The team in Post Position 1 starts by playing Post 2; the winner scores a point and stays on the court to play Post 3, and so forth. After Post 8 has played one point, the rotation starts again, but now each "point" scores as two points. When one team has accumulated seven points, the game is over.

Obviously, the team in the starting post positions have a great advantage. Those in Posts 7 and 8 may only get one swing of the cesta in an entire game. So to equalize the chances of the teams, the stronger ones are always assigned the disadvantageous posts.

This method of seeding works all too well; it helps make jai-alai a game that cannot be handicapped well. At horse tracks and dog tracks, bettors regularly try to dope out the winner of a race in a rational fashion; that is the appeal of the games.

But a jai-alai bettor will almost never be heard to say, "I think Umberto and Zoqui are a cinch in the ninth game." Anyone making such a statement could be reliably diagnosed as loco.

Jai-alai is a numbers game. It is remarkably popular with the members of Miami's gypsy community, who attempt to use numerology to pick winners. As one bettor explained it, "In jai-alai, everything is equal except the probability of certain number combinations."

As the game is structured, certain results are more probable than others. A finish of 6-8-7 in a jai-alai game is practically impossible; 3-1-5 is relatively commonplace.

Serious jai-alai gamblers attempt to compute these probabilities, weigh them against the odds and bet the optimal combinations in quinellas, perfectas or trifectas. (Quinellas and perfectas require the bettor to pick the first two finishers in a game. In the trifecta, he must pick the first three finishers in order).

Because of the difficulties involved in handicapping, jai alai does not attract many serious bettors. In Miami, for example, the majority of the patrons are either tourists or Latin aficianados of the sport.

Game-fixing in jai alai is harder to detect than in many other sports.

In horse racing, for instance, illogical results may be readily apparent. A jockey may have to make a very visible and suspicious effort to restrain a half-ton animal from running as fast as possible.

But in jai alai, there is no such thing as an illogical result. No one will get suspicious because a player fails to catch a ball whizzing over his head at 150 miles an hour.