As marketing leaders amass rich and detailed records of the interests and intents of their customers, the value they can derive from second-party data — by intelligently patching into other brands' data — only grows. Marketing leaders' interest in this type of data sharing is growing, but large questions remain unanswered: How do marketers look for other brands' data, for what purposes should they use it, how do they make contact, and what pitfalls do they need to avoid? This report will describe the nature and value of second-party data sharing, how marketers should use it, how they should get going, and which partners they should work with.