Small number of Drosophila melanogaster populations from two distinct geographical regions of Turkey, Central Anatolia and Black Sea, were studied. Populations sampled were electrophoresed for a single locus, alcohol dehydrogenase (Adh) to assess population differentiation. Both the magnitude of genetic differentiation levels and the population structure based on hierarchical F-statistics allow populations to be grouped on two genetically divergent area, Central Anatolian and Black Sea. One ecological correlate, average yearly maximum rainfall, R-year seems to track this Adh genetic variation pattern. The study also shows that a typical pattern of geographical Adh polymorphism, can emerge with a handfull of populations sampled across a relatively small distance.