Cowden syndrome (CS), an autosomal dominant disorder, is associated with germline mutations of the PTEN (phosphatase, tensin homolog, deleted on chromosome TEN) gene. PTEN mutations were linked to several human neoplasms. Clinical diagnosis has been based on Consortium criteria, but detection of mutations in the PTEN gene has importance in accurate diagnosis. This article presents a female patient with classic features of the syndrome and gives the result of first PTEN mutation analysis result in a Turkish CS patient. The patient, who suffered from trichilemmomas, papillomatous lesions, lipomas, thyroid lesions, gastrointestinal hamartomas, and fibrocystic disease of the breast, is consistent with the diagnostic criteria of CS. The exons and intron/exon boundaries of the PTEN gene were analyzed by polymerase chain reaction and direct sequencing. We analyzed the clinical features and DNA in a Turkish patient with CS. We found a single-nucleotide substitution in the splicing acceptor site of intron 5 of the PTEN gene (IVS5-2A > C). It is not clear whether which types of PTEN mutations are responsible for particular phenotypes. This germline PTEN mutation, IVS5-2A --> C, has been reported once before, but the clinical features differ from our patient. Also, this is the first reported PTEN mutation from Turkey.