LAS VEGAS — from www.nytimes.com – Most of the familiar spectacles are likely to be on display here this week during the International Consumer Electronics Show: the acres of flat-screen televisions, the 140,000-or-so smartphone-packing attendees, the grim, never-ending taxicab lines. Something will be missing, though.

In a rare disruption of two yin-and-yang forces, C.E.S. will not coincide this year with the Adult Entertainment Expo, a trade show and fan event. This is only the second time in recent memory that the event will not overlap with C.E.S., said Brian Gross, a spokesman for AVN, the publishing company that produces the conference.

Instead, the Adult Entertainment Expo will take place Jan. 18 to 21, culminating on its last day with an awards show known as the Oscars of the business, the AVN Awards.

In a statement, Theo Sapoutzis, chief executive of AVN, said that because C.E.S. did not overlap on a weekend this year, that would have altered the “date pattern of AVN and the AVN Awards,” the latter of which typically occurs on a Saturday night. “This caused everything on AVN’s part to be moved to later in the month,” he said, adding that AVN would like its event to coincide with C.E.S. in the future.

C.E.S. and the Adult Entertainment Expo have long existed side by side, not always amicably. Long ago, the two shows were, in fact, one, said Paul Fishbein, the founder of AVN, who sold the company two years ago. When Mr. Fishbein started his business in 1983, the movie producers and distributors it covered began gravitating toward C.E.S., where the videocassette recorder was stirring up the home video industry. Pornography played a meaningful role in stoking demand for the first VCRs.

Companies began exhibiting at C.E.S., but many felt marginalized by the show, Mr. Fishbein said. In Las Vegas, they were often exiled to a basement exhibition space in the Sahara hotel, and at another C.E.S. event in Chicago in June they were forced to exhibit in a tent that had no air-conditioning, he said.

In the late ’90s, Mr. Fishbein decided to form the Adult Entertainment Expo as a separate event that occurred around the same time as C.E.S. in Las Vegas and the two shows settled into a comfortable coexistence. Once they grew tired of gadgets, many of the C.E.S. conventiongoers would wander over to the other show to have their favorite performers sign autographs. Mr. Fishbein said AVN conducted a survey of attendees to its show several years ago and found that about 30 percent of the traffic on the “fan days” at the show came from those who had also attended C.E.S.

“It was a tradition,” Mr. Fishbein said. “Everyone was used to it.”