Introduction. In Algeria, the Mediterranean fruit fly Ceratitis capitata Wiedmann constitutes the main obstacle to production and exportation of many fruits. In studies of the genetic structure differences of medfly populations, certain authors, using molecular markers, observed the existence of different patterns among the pest Mediterranean populations. A clear understanding of the source and migration of the Mediterranean fruit fly would be useful for undertaking a successful eradication or control program. For this reason, preliminary work sought to compare the genetic structure of Algerian populations of C. capitata with that of other populations situated either in the western Indian ocean or on the northwestern Mediterranean coast. Materials and methods. The study of enzyme polymorphism allowed the comparison of the genetic structure of four Algerian populations of Ceratitis capitata with one from Reunion Island and five other populations collected from the northwestern Mediterranean coast (France and Spain). Enzyme analyses were performed on ground pest adults electrophoresed on a starch gel. Fifteen loci were analyzed for each population. Results and discussion. In spite of a wide geographic distribution of the analyzed populations (from a latitude of 24° to 44° N), no gradient of allelic frequencies was observed for any of the polymorphic loci. A higher genetic variability was observed in the population of Reunion Island than in the populations of Algeria or the northwestern Mediterranean coast. No genetic differentiation was observed among the populations of southern Algeria (Djanet and Ghardaïa) and northern Algeria (Boufarik and Oran).