ROCKVILLE, Md. (AP) _ The chic red garbage bags used by some suburban homeowners are sending the wrong signal to local trash haulers, who are trained to recognize red color- coding as a warning for infectious wastes.

''It was a dumb thing for Neiman-Marcus to do,'' said Alan Bergsten, chief of Montgomery County's Division of Solid Waste Management, of the red bags emblazoned with the Neiman-Marcus logo in black lettering.

''Red bags mean something very special to us. As far as I know it is a nationwide practice,'' said Bergsten. ''It's a generally accepted item in the solid waste business. If there are a whole lot of them out there, they're going to give us a fit.''

The Trash Sack is advertised as ''the neat, convenient and fun way to dispose of trash,'' by Neiman-Marcus, a Texas-based upscale retailer, which has a store just across the county line in northwest Washington.

A sales clerk said the bags are a ''hot seller'' this season, at $5 a packet for the 13-gallon size and $6.25 a packet for the 33-gallon size.

But health officials see nothing hot about them.

''It's going to cause a problem, no doubt about it,'' said Ray Feldmann of the state Department of Environment in Baltimore.

Store spokeswoman Barbara Ann Kelly said corporate policy forbade her from discussing the matter and referred questions to store headquarters in Dallas. Associates of Jan Roberts, Neiman Marcus' corporate vice president for public relations, said she was unavailable.

Waste management officials fear some garbage workers may become squeamish about the bags because of rising fears of coming in contact with waste materials from patients with acquired immune deficiency syndrome or AIDS- related illnesses.

''This stuff is not even supposed to leave a hospital,'' Bergsten said. ''A red bag means that bag stays in-house.''

He said that in the three or four cases annually that the hospital bags turn up in the county, workers sort through the items to identify the hospital, then ask the hospital to retrieve the materials.