The number of mobile phone subscribers reaches 4 billion.
The increase has been especially strong in developing countries like Brazil, China and India, which have been able to provide cellular phone service to tens of millions of people much more cheaply than having to wire up homes and offices for fixed-line telephones.
"By the end of 2006, there were a total of nearly 4 billion mobile and fixed-line subscribers," said the International Telecommunication Union in a 227-page report, "Trends in Telecommunication Reform."
In 1996 there were fewer than 1 billion fixed-line and mobile phone subscribers altogether. Fixed-line subscriptions have grown slowly since then, but mobile has taken off, showing "spectacular success," said Doreen Bogdan-Martin, one of the report's authors.
The total includes 1.27 billion fixed-line subscribers and 2.68 billion mobile subscribers, the report said, adding that 61 percent of the world's mobile subscribers are in developing countries.
China and India have been growing especially fast. The two countries together added almost 200 million more mobile subscribers to the global total in the first three months of this year - India had 110 million new subscribers in the first quarter and China 87 million.
Although the least developed countries lag behind, growth is picking up in Africa, which the agency is trying to encourage.
The report said more than 1 billion people in the world use the Internet.
Thanks to advances in technology that enable fast "broadband" connections over mobile phones, Africa has the prospect of being able to offer its people good Internet connections without having to use fixed-line connections favored in developing countries, it said.
"There's also been significant growth in broadband services, where nearly 280 million broadband subscribers have been added in the past six years alone," said Bogdan-Martin.
"Fixed-line broadband overtook dial-up Internet access subscribers in 2005, and the numbers of wireless broadband subscribes are also growing," she said.
Improved access is coming in what the telecommunications industry calls "next generation networks" - using either fixed or mobile connections - which can offer services including television and "voice over" Internet long-distance phone calls.
The report said countries may need to change their regulatory requirements to remove obstacles to innovation and investment if the benefits of new generation networks are to be realized.
"In many countries, licensing practices would prohibit operators from offering a popular 'triple play' of voice, broadband and IPTV," said Susan Schorr, chief author of the report.