But pay-HDTV expanding fast in the US.
Japan has more high definition TV viewers than any other nation but the US is fast catching up, according to new research.
More than 9.2 million Japanese homes will be watching HDTV broadcasts by the end of 2007, predicts US-based research firm SNL Kagan.
Japan has considerable experience in high definition broadcasting spearheaded by research at giant national TV company NHK.
While HDTV technologies in other countries were still at the trial stage, Japan had moderate success with an early analogue broadcast HDTV system in the 1980s and 1990s.
This helped to prepare programme makers and audiences for the lower cost digital HDTV systems developed in the past few years.
However, after a slow start, HDTV uptake in the US is growing fast, according to SNL Kagan, and will surpass Japan with 12 million HDTV-equipped homes by the end of 2008.
SNL Kagan figures suggest that there are currently six million homes in the US receiving HDTV broadcasts.
This rapid growth in the US is being driven in part by investment from pay-TV operators.
"Operators are looking for any possible means to get an edge on the competition. In addition to providing a new revenue stream, a strong HDTV line up offers a powerful bragging right," said Ben Reneker, a senior analyst at SNL Kagan.
"As competition between cable, satellite and IPTV intensifies, high-definition programming becomes increasingly important."
The involvement of public broadcaster NHK means that HDTV programming in Japan tends to be free to view.
The US, Canada and France all have considerably larger markets for pay-HDTV, according to Reneker.