Although researchers have chronicled the high rate of entrepreneurship in Chicago among recent Asian immigrants, especially Koreans, few studies examine groups with low rates of self-employment, such as Mexicans. In this article we analyse a unique survey of business owners operating in an immigrant community to identify circumstances that help and hinder entrepreneurship by comparing the experiences of Mexicans, with those of Koreans. We find that Korean and Mexican business owners draw on thinner ethnic social networks and do not reap similar advantages from co-ethnic business dealings. Until Mexicans consolidate a market niche, their opportunities to benefit from ethnic vertical integration will remain limited.