Managers invariably use their personal contacts when they need to, say, meet an impossible deadline or learn the truth about a new boss. Increasingly, it's through these informal networks--not just through traditional organizational hierarchies--that information is found and work gets done. But to many senior executives, informal networks are unobservable and ungovernable--and, therefore, not amenable to the tools of management. As a result, executives tend to work around informal networks or, worse, try to ignore them. When they do acknowledge the networks' existence, executives fall back on intuition--scarcely a dependable tool--to guide them in nurturing this social capital. It doesn't have to be that way. It is entirely possible to develop and manage informal networks systematically, say management experts Cross and Prusak. Specifically, senior executives need to focus their attention on four key role-players in informal networks: Central connectors link most employees in an informal network with one another; they provide the critical information or expertise that the entire network draws on to get work done. Boundary spanners connect an informal network with other parts of the company or with similar networks in other organizations. Information brokers link different subgroups in an informal network; if they didn't, the network would splinter into smaller, less effective segments. And finally, there are peripheral specialists, who anyone in an informal network can turn to for specialized expertise but who work apart from most people in the network. The authors describe the four roles in detail, discuss the use of a well-established tool called social network analysis for determining who these role-players are in the network, and suggest ways that executives can transform ineffective informal networks into productive ones.