The truth, Mr. Vidallier said, as he stopped laughing, is that Cajuns, like many other Americans, are being assimilated into a broader, blander, rootless culture -- but not so fast as the census survey hints.

''Your average American kid grows up in Cleveland, marries a girl from Texas and settles in Kansas,'' Mr. Vidallier said. ''Your average Cajun boy grows up in Crowley, marries a girl from Ville Platte and settles somewhere close to her mama. In Eunice. We tend not to stray so far.''

The latest data was derived from a Census 2000 Supplemental Survey of 700,000 United States households, including residents in 35 counties in Louisiana, some of them heavily Cajun. The survey reported that 44,103 people in Louisiana identified themselves as Cajuns, compared with 407,319 in the 1990 census. The picture might become clearer when full ancestry data from the census is released in two or three years.

One census analyst said the answer to the decline might be a simple matter of the way the survey forms were worded and interpreted.

''We're trying to figure out what's going on,'' said Angela Brittingham, an analyst in the office of ethnic and Hispanic statistics at the Census Bureau.

Since 1980, the census form has asked, ''What is your ancestry or ethnic origin?'' with space for a written answer. To guide respondents, the form gives several examples, which change from census to census. In 1990, ''Cajun'' was a listed example, which could explain why so many Louisianians gave that answer, Ms. Brittingham said. The 2000 census dropped the Cajun origin but added ''French-Canadian,'' she said.

And those who wrote in their ancestry as ''Cajun French,'' as some Cajuns consider themselves, may have been classified French-Canadian by census workers, Ms. Brittingham said.