TRAVELING ALONE has a bad reputation. Tell someone you are going away on a vacation by yourself, and they look at you as if you are the world's great loser. "How sad," they think, "how lonely."

The world is full of single travelers who would disagree. They have a way of almost inevitably linking up with one another on a plane, in the compartment of a European train, on an afternoon's guided tour. Shared confinement makes for quick friendships.

Pairs or groups traveling together, with companionship readily at hand; tend to get wrapped up in each other. Singles, having no one at hand to share their experience with, seem more open to friendly overtures, and so the opportunities to meet new people can be greater.

These brief encounters may bring only a beer at a sidewalk cafe with a congenial stranger or a morning's visit together to a famous site. When that happens, though, you are no longer really alone.

Any number of reasons may prompt you into setting out on your own.

You have planned for a year to explore France, only to see your traveling companion drop out at the last moment. Why should that stop you?

Your great dream is to bounce down the rapids of the Colorado River in a raft, an idea that appalls everyone you know. You can't wait forever for someone to share all your enthusiasms.

You are no longer a part of a couple who went everywhere together. That doesn't mean you shouldn't take a vacation on your own.

Some people can ramble for many weeks by themselves across a continent. No stuffy museums if you don't like them; or the reverse, a full day of museums and nobody to complain. But such a trip can be hard and not undertaken lightly.

Popular alternatives are singles tours and cruises. At a group table, you seldom dine in wistful silence.

Adventure travel attracts singles, mostly the young but not necessarily so. The out-of-doors can be a rewarding vacation for the socially shy. On a whitewater raft, everybody's equal as a beginner. Good-humored participation counts most here.

Only the other day, a single businessman in his early thirties (and between relationships) was explaining why he hadn't taken a vacation in almost two years. "It's no fun when you have to go by yourself," he sighed. He couldn't have been more wrong.