If you have been to the race track recently, chances are you ran into a number of people you have seen there before.Racing, more than any other sport, draws on a relatively small number of fans who attend over and over and over.

Only three in 10 Washington area residents 16 years old or older have gone to a horse race in the past 10 years, according to a Washington Post survey, and only one in 10 has gone more than once a year. But that one in 10 makes for a core of devotees whose characteristics are distinct from those of all other sports fans.

In this age of television, and with the emergence of "new" sports in Washington, people often develop an interest in an activity without ever going to see it played professionally. Just that seems to be occurring with tennis, hockey and soccer - sports that claim high percentages of followers in playgrounds or on TV who have never been out to watch a pro contest. Not so for horse racing.

Only one person in seven who expresses an interest in horse racing has not been to the races in the last 10 years. At the same time, one in every five race horse followers who has gone to the track once during that period has gone at least 100 times. Such intensity of spectator interest is unmatched by those who follow football, basket or any other sport.

Traditionally, horse racing means gambling, and the myth has been that those who can least afford to lose are the ones who gamble the most. The Post survey suggests that the myth is grounded in reality.

Because only 11 per cent of the 1,017 persons interviewed in the survey listed horse racing as among their favorite sports, the numbers are too small to draw a conclusive portrait of racing fans. But the trend seems clear:

Of those with annual family incomes of $30,000 or more, 5.6 per cent list horse racing as a favorite sport; for those with annual family incomes between 18,000 and $30,000, the corresponding figure is 8.2 per cent; for those with annual family income between $10,000 and $18,000, 14.6 per cent, and for those with annual family income of less than $10,000, 15.2 per cent.

One way of reading those figures is to say that the poorest in the community are almost three times as likely to be partial to horse racing as are the most affluent.

At the same time, there is an indication that people take to horse racing at periods in their life when they can most afford to, regardless of their income. The age groups most inclined to select horse racing as a favorite sport are those between 21 and 25 years, of age, and those older than 50. There is a slight but conspicuous fall-off of interest, then, in the years in between, when people are raising children.

Interest in racing appears evenly distributed among blacks and whites in the survey. It also appears evenly distributed in the District of Columbia and the Maryland suburbs, but interest lags somewhat in Northern Virginia.