We review the empirical literature on ethnic economic enclaves after the concept was formulated 25 years ago. The balance of this literature is mixed, but many studies reporting negative conclusions were marred by faulty measurement of the concept. We discuss the original theoretical definition of enclaves, the hypotheses derived from it, and the difficulties in operationalizing them. For evidence, we turn to census data on the location and the immigrant group that gave rise to the concept in the first place - Cubans in Miami. We examine the economic performance of this group, relative to others in this metropolitan area, and in the context of historical changes in its own mode of incorporation. Taking these changes into account, we find that the ethnic enclave had a significant economic payoff for its founders - the earlier waves of Cuban exiles - and for their children, but not for refugees who arrived in the 1980 Mariel exodus and after. Reasons for this disjuncture are examined. Implications of these results for enclave theory and for immigrant entrepreneurship in general are discussed.