Lek mating systems are relatively rare but occur in a diverse taxonomic array of animals, including birds, mammals, anurans, and insects. Such systems exhibit four features: 1) males provide no parental care and supply only gametes; 2) males are spatially aggregated at mating arenas (or leks); 3) males do not control access to resources critical to females; and 4) females are free to select mates at the arena. Among insects, fruit flies of the families Tephritidae and Drosophilidae display lek behavior that closely resembles the 'classic' lek mating systems of vertebrate species. The objective of this paper is to provide an overview of empirical findings on lek-forming tephritid and drosophilid flies. The essay is organized around a series of 19 questions, the first six of which provide background information on fruit fly leks. These questions deal with the location, persistence, and size of leks as well as pheromonal attraction of females and the nature of male-male aggression. The remaining questions touch on broader issues that are common to the study of lekking species regardless of taxonomic affiliation. For example, these questions concern skewed mating distributions among males, male signals important in female choice, the importance of male aggression and signaling position in affecting male mating success, the possibility of male choice, costs to males associated with lek displays, and evidence of direct and indirect benefits to females resulting from mate selection etc. Reflecting data availability, emphasis is on precopulatory mate choice, sperm competition and female cryptic choice are briefly addressed.