Cowden disease is an autosomal dominant disorder associated with an increased risk of breast, thyroid, and skin cancer in which germline mutations in a candidate tumour suppressor gene (PTEN) have been identified previously. Sjögren's syndrome is a chronic inflammatory and autoimmune disorder of exocrine glands for which the genetic basis is unknown. This report describes a novel PTEN mutation (L139X) in a patient with Cowden disease and Sjögren's syndrome. This observation raises the possibility of a link between mutations in the PTEN gene and Sjögren's syndrome.