Silverlight 4 and its related tools for Developers are read now. Check out all download instructions here.
Ensure that you have the latest Visual Studio 2010 or Visual Web Developer Express 2010 installed as it is a prerequisite for developing Silverlight 4 applications using Visual Studio. Below are the additional tools you’ll want to get started:
Once you have the tools you need to get started, view more information below to walk you through some of the new features in detail and download some sample code.