The truck pulled out of Cochabamba in the fading light of an April evening, rolled into the gentle countryside that surrounds Bolivia's second largest city, and began to climb.

We were already at 8,400 feet, high enough to make breathing painful, but now we were grinding our way relentlessly toward the altiplano. The road narrowed to one dirt lane, and turned corkscrew. As we swung away from the rock wall on one side to skirt the unguarded shoulder, I could see the crumpled remains far below of trucks that had failed to negotiate one sharp curve or another.

By midnight the climbing stopped and descent began. We twisted our way slowly down through the clouds and into a tropical rain forest, thick with huge trees and dangling vines and great, deep-green leaves.

Then, at a point obviously predetermined but unaccompanied by explanation, the driver stopped and shut off the engine and lights. He went to sleep, leaving me to reflect on my search for a true South American adventure. Behind lay 10 hours of bouncing in that truck; ahead, a jungle village and a three-day cruise up the River Beni.

I was sure the best was yet to come.

It seemed only minutes before the driver awoke, but color was filling the sky. Within a mile we were out of the jungle, and part of a parade of trucks approaching the little village with the exotic name of Porto San Francisco.

Primitive would be more accurate. There were a dozen shacks. The largest claimed to be a hotel; three others had the unmistakable look of bars. All were one-story, their walls made of wood planks so loosely connected that the morning light shown through. Roofs were constructed of palm fronds laid flat on bamboo frames.

The scene at the water's edge was classic foreign cinema. The murky river emerged from a jungle still black from night, turned a big "U" at the village and returned to the endless tangle of haunting trees. Eight or nine boats jammed into that bend. Bolivia has no outlet on the ocean; most of its bulk cargo travels by river boat.

The boats resembled those from Mark Twain's Mississippi, but were driven by powerful diesel engines. They were 50 to 60 feet long; their double decks were made of wood. Freight rode below, with the top deck reserved for cabins and the bridge. Most towed barges.

Their cargo -- cattle, wood and raw rubber -- had already been taken ashore. Now shoes and tires, crops and beer were being unloaded from the trucks and onto the boats in a frenzy of activity.

I sought out my captain for news of our departure. He viewed the work on shore, and counted trucks.

"Maybe today," he shrugged. "Maybe no."

His message was clear: When his boat was full, we would leave.

It was getting hot, but the Indians who call Porto San Francisco home were busy unloading and then reloading the trucks. Meanwhile, naked children ran from hut to hut, playing; mothers fetched water from the river, washed clothes and nursed infants.

The rivermen sat around and waited. They waited in the bars, or took their rifles into the jungle to stalk snakes and lizards, and especially the beautiful, long-tailed parrots.

And I waited, sitting on a dugout on the shore.

As evening approached, the first of the loaded trucks lined up at the port official's hut in curious fashion. Suddenly I realized why we'd had to stop on the ride in.

"One-way road," my boat captain confirmed, explaining that the government changed the direction of the road every 12 hours, and decided when the port was open and closed.

"The government," he said, and flicked his hand in the air.

Two more trucks sped in at sundown, just before a man in Army-surplus fatigues signaled the newly loaded trucks to head out.

The unloading ritual began anew. It was getting buggy, so I repaired to one of the bars for a dinner of greasy chicken and warm beer, and to wait.

The bar was hot, and not very busy. The captain was there, drinking beer and looking through the screens at the cloud of mosquitoes outside. At one table two truck drivers rolled dice from a leather cup; at another, two rivermen slapped dominoes down hard on the crude, wooden table.

I moved beside the captain, and bought him another beer.

"Are there enough trucks to fill the boat?" I asked.

"Maybe yes," he shrugged, "maybe no."

A large, black mosquito settled on my arm. I slapped at it, but it was too fast.

"But tomorrow for sure," I urged.

"Official say holiday tomorrow," he said. "Port closed."

"But the next day?"

"Maybe."

I slapped at another mosquito as the two men playing dice rose to leave, their truck fully loaded.

"Cochabamba?" I called, making an international gesture with my thumb.

"Si."

"You've got a passenger!" Skip Rozin is a writer who lives in New York. More Turkeys, Page E4.