Dominant economic theories of black market research do not sufficiently explain why East Indian merchants in Belize City are particularly active in Belize's foreign-exchange black market. This article develops a sociological theory depicting black markets as social structures and relates the structure of ethnic trading networks to the demand for black money by focusing on the crime of underinvoicing. The author describes the East Indian network, then discusses the evolution of ethnic black markets more generally. Table, appendixes, notes, references