Cowden syndrome (CS) is an autosomal dominant inherited disorder characterized by hamartomas in a variety of tissues including the skin, thyroid, breast, endometrium, and the brain. Individuals with CS are predisposed to development of malignancy in these organs, especially the breast and the thyroid. We describe 3 unrelated individuals with CS associated with germline PTEN mutations. While the frameshift (375insTTTA) and the missense (Gly69Arg) mutations reported herein are novel in CS, the nonsense (Arg130stop) mutation has been described in 2 families with CS and in a single family exhibiting both CS and Bannayan Zonana phenotype.