Verticillium dahliae has been recently characterized as a heterothallic fungus having two MAT idiomorphs, MAT1-1 and MAT1-2, which suggested that a putative sexual life cycle of the pathogen might exist. A successful mating in heterothallic fungi requires two individuals of opposite mating types present together in the same site. Co-occurrence of both mating types of V. dahliae has been investigated in many parts of the world but not comprehensively in Turkey. This study aims at determination of the mating types in V. dahliae populations in the major cotton producing districts of Aydin Province. A total of 123 V. dahliae isolates obtained from cotton were subjected to PCR assay with the two pairs of specific primers for mating type determination. All of the isolates produced a single amplicon approximately 600 bp in size, which is known belonging to MAT1-2 idiomorph. The results suggested that MAT1-1 has not been introduced yet to the Aydin Province. Absence of MAT1-1 idiomorph will deprive the pathogen from sexual reproduction and this maintains that the pathogen population remains clonal with presumably having low levels of genetic diversity.