The cell phone penetration rate for Japan will likely hit 65.5 percent in 2006, up from 52.8 percent at the end of 2001, research and consulting firm Gartner Japan Ltd. said Wednesday.

The diffusion rate translates into an estimated 83.96 million cell phones in use by 2006, up from 67.10 million at the end of 2001, the Japan unit of U.S.-based GartnerGroup Inc. said.

Nahoko Mitsuyama, an analyst at the Tokyo-based firm, said that although the Japanese cell phone market has already matured, it will probably continue to grow slowly over the next five years.

Gartner Japan also estimates revenues from cell phone services will rise to 7.8 trillion yen in 2006 from 6.3 trillion yen in 2001 due to increased use of data communications services, such as Internet access and e-mail.

"There is no doubt that the traffic volume of data communications via cell phones, including receiving and sending videos, will increase dramatically," Mitsuyama said.

"But revenue growth from such services will not be as dramatic as the traffic increase, because cell phone operators will be obliged to reduce communication charges sharply to promote them," she added.

Gartner Japan expects revenues from data communication services to account for 20 percent of overall cell phone service revenues in 2006.