Duke University’s Fuqua School of Business disciplined 34 first-year Master of Business Administration students who were caught in the school’s largest cheating scandal.

Fuqua investigated 38 students, a marketing professor who oversees the school’s judicial panel, Gavan Fitzsimmons, said in an email. Four students were cleared and 34 others received disciplinary action ranging from expulsion to failing grades.

The cheating allegations are the largest to hit a top American business school since 2005. Business schools have been strengthening their ethics curricula after corporate scandals at Enron Corp. and WorldCom Inc., which landed the companies in bankruptcy and their leaders in jail. Fuqua posts an Honor Code that covers cheating in every classroom.

“We place these words prominently in our classrooms because they represent our core values as an institution,” dean Douglas Breeden said in a statement. “Fuqua depends on every member of its community to uphold the code in both spirit and action. This is why we require, as a condition of enrollment, that all students acknowledge their personal acceptance of the code.”

In 2005, the Harvard Business School, Massachusetts Institute of Technology’s Sloan School of Management, and others rejected 150 applicants who tapped into an online database to see if they had been accepted.

Fuqua should be praised for going public with the results of its judicial board, the executive director of the Dartmouth College Ethics Institute in Hanover, N.H., Aine Donovan, 50, said.

“Duke is doing as good a job as anyone to prevent cheating,” Ms. Donovan said. “They really lead the way on the honor code. Duke really makes a big deal out of their honor code.”

Nine students face expulsion and 15 face a one-year suspension and a failing grade in the course. Ten others were found guilty of lesser offenses, nine of whom received a failing grade and one who flunked the assignment, Mr. Fitzsimmons said in the e-mail.

“It is clearly disappointing,” associate dean Michael Hemmerich said in a telephone interview yesterday. “This is something that really stood out.”

Mr. Hemmerich said the students’s names couldn’t be released because of federal privacy protections. The professor and the course, which is required, won’t be identified.

The students are still enrolled and have about five weeks to appeal their cases, Mr. Hemmerich said.

The results of the judicial board’s hearings were disclosed in an email to the campus on Friday.

The incident happened about six weeks ago, Mr. Hemmerich said. Fuqua divides its school year into four six-week terms. The school’s fourth term is ending now, and the cheating took place during the third term.

The course professor noticed similarities in answers given by some students on a take-home exam, Mr. Hemmerich said.

The 410 members of the class of 2008 had an average age of 29 and almost six years of work experience before being admitted to the two-year program, according to Fuqua’s Web site.