xingzoomlogo011708.pngEuropean business networking site XING and U.S. business search service ZoomInfo are introducing a way to bring their two continents’ worth of business contacts together to challenge rival LinkedIn as well as more general social networks like Facebook.

Starting tomorrow, XING members will be able to search for and befriend more than 18 million business professionals who have registered profiles on ZoomInfo and search a total pool of 40 million profiles (including unregistered ZoomInfo profiles) who don’t use XING. With this search option, the two companies are hoping to spur more social interaction. Search results will include people’s career history and professional highlights. Seeing this information about somebody may give you more reason to want to friend them within XING.

XING is small in the U.S. but popular in Europe and claims four million total users worldwide. ZoomInfo is not really a social network, as it scrapes web pages for information about the people in its database rather than relying on friend requests. Because it gathers information about businesspeople with or without their permission, it’s been more useful for recruiters than for professional interaction.

The new search offering is the second step in the two companies’ effort to present an international alternative to big business networking site, LinkedIn. The companies announced their partnership, including this search feature, last June (our coverage). The first step came in September, when ZoomInfo introduced a co-registration option so that people could register simultaneously for both its site and XING. ZoomInfo also introduced a public application programming interface for developers at that time, so other developers can create applications within its platform (our coverage).

Hamburg, Germany-based Xing, which went public last year, Waltham, Mass.-based ZoomInfo, and LinkedIn are also no doubt concerned that businesspeople are using more general social networks like Facebook for business networking. Anecdotally, I’m finding that Facebook is just as useful for business networking.

Linkedin, last I heard, has more than 16 million total registered users and says it is growing by around a million registered users a month. Facebook has more than 61 million monthly active users, although it’s not clear what portion of those people are using Facebook for business.