Microsoft and Yahoo have completed their "Search Alliance" transition in the U.S. and Canada. 

"As of today, adCenter powers 100% of paid search advertisements on both Bing and Yahoo!, partner sites and publisher networks in the U.S. and Canada," Yahoo and Microsoft said in a joint message to WebProNews. "The search alliance creates a competitive alternative in search, allowing advertisers to reach a combined audience of 163 million searchers in the U.S. and 15 million searchers in Canada via Bing and Yahoo! Managing a single account for both Bing and Yahoo! will let advertisers save time and simplify their campaigns."

"The transition comes after months of testing and collaboration between Yahoo! and Microsoft, with strict attention being paid to protecting the quality of experience for publishers and advertisers during the upcoming holiday season," the companies said. "The paid search transition comes on the heels of both companies completing the transition of the back-end technology for English-language Yahoo! organic search results in the U.S. and Canada in August."

Yahoo and Microsoft say that next up, Yahoo Mobile search ads will be transitioned to the Microsoft platform by the end of October. They will then start transitioning international markets next year, with all global customers and partners expected to be transitioned by early 2012. 

"The organic search transitions will occur first on a market by market basis with paid search to follow," the companies said. "For organic search, the search alliance intends to start with our Spanish-speaking Latin America markets in Q1 2011; for paid search, the next set of markets will be UK, France, Ireland and India in Q2 2011."

Last month, data from Nielsen showed that Microsoft had taken the number 2 spot in search market share in the U.S. for the first time, and that was even without Yahoo’s help. 

The companies intended to have the transition ready in the U.S. before the holidays, and it appears that they achieved that.