Alfred E. Neuman finally has a reason to worry.

Mad magazine, the class clown of American publishing, is being shuffled off to the periodical equivalent of an old-folks home at the age of 67.

After the next two issues, a publication that specialized in thumbing its nose at authority will no longer include new material, except in year-end specials, according to two people with knowledge of the decision. Instead, the “usual gang of idiots,” as the staff has long called itself on the masthead, will fill the magazine’s pages with old material.

A giddy creation of the staid 1950s, Mad hit a circulation peak of 2.8 million in 1973. Since then, it has steadily lost readers and relevance, a victim of its own success, as its skeptical, smart-alecky sensibility became dominant in American popular culture. “Saturday Night Live,” “The Simpsons,” “South Park” and The Onion can be counted among its heirs, and the magazine influenced a generation of comedians and comic artists, from the late-night host Stephen Colbert to the comics writer Art Spiegelman.

“Mad was, ‘The entire adult world is lying to you, and we are part of the adult world. Good luck to you,’” Mr. Spiegelman said in an interview on Friday. “I think that shaped my entire generation.”