The list consists of 156 companies, accounting for 97 percent of what Apple says it pays to its suppliers. Apple’s tally of its suppliers includes many big-name companies like Intel and Nvidia, both makers of chips for Apple’s Macintosh computers, along with other parts makers like Samsung Electronics, Toshiba and Panasonic. The list also includes less recognized companies like Zeniya Aluminum Engineering, Jin Li Mould Manufacturing and Unisteel Technology.

But the list excludes many of the secondary suppliers — companies that provide parts to firms that directly contract with Apple. For instance, though the American glassmaker Corning has manufactured the strengthened glass in iPhones, it does not appear on the list because it technically does not contract with Apple, but with an intermediary that finishes the glass before it is delivered to an assembly factory.

Apple said 229 audits were conducted as part of this year’s supplier responsibility report, an 80 percent increase over the number the year before. The company said the facilities where repeat audits were done had shown fewer violations.

In an e-mail to Apple employees, Timothy D. Cook, the chief executive, said Apple had used its influence to improve living conditions for the people who make its products, including employee housing. “To meet our requirements, many suppliers have renovated their dorms or built new ones altogether,” he wrote.

This is the sixth such report Apple has issued. The company began conducting audits and publishing reports after news articles in 2006 showed poor working conditions at Foxconn, a Chinese manufacturer of Apple products.

Apple said in the report that it recently became the first technology company to join the Fair Labor Association, a nonprofit group that aims to improve conditions in factories around the world. Apple said it would allow the association’s auditing team to gauge the performance of Apple’s suppliers against a code of conduct and publish the results.

“We welcome Apple’s commitment to greater transparency and independent oversight, and we hope its participation will set a new standard for the electronics industry,” Auret van Heerden, the association’s president, said in a statement.