This paper provides an overview of major transmission planning activities related to wind integration studies in the United States and Europe. Transmission planning for energy resources is different from planning for capacity resources. Those differences are explained, and illustrated with examples from several regions of the United States and Europe. Transmission planning for wind is becoming an iterative process consisting of generation expansion planning, economic-based transmission planning, system reliability analysis, and wind integration studies. A brief look at the policy environment in which this activity is taking place is provided. A set of coherent and collaborative transmission planning, siting, and permitting policies and cost allocation method must be developed to achieve the intended objectives. The scale of transmission development envisioned for this purpose will require unprecedented cooperation across multiple jurisdictional boundaries.