In August 2008, the U.S. Census Bureau sponsored a supplement to the monthly Current Population Survey (CPS) questionnaire. The Immigration/Emigration Supplement, also referred to as the Migration Supplement, included questions on five topics – citizenship, year of entry, residence one year ago, residents and emigrants abroad, and monetary transfers. The purpose of this paper is to provide data users with additional information about the Migration Supplement that is not found in other published sources. This paper begins with a short overview of the Current Population Survey, providing some basic information necessary to understand the structure of the Migration Supplement questionnaire and the advantages and limitation of the data collected by this instrument. It then discusses the goals and content of the Migration Supplement and briefly reviews the dates and method of administration, universe, sequencing of the five sections, information about the number of eligible and interviewed households, and overall survey response rates. The remainder of the paper discusses each section, explaining the goals, questions, universes, and skip patterns within and among the sections. This paper concludes with information about the availability of the public use microdata files and other related metadata documentation.