Cowden's disease is a multisystem disease complex inherited as an autosomal dominant trait with incomplete penetrance and variable expressivity. Its mucocutaneous findings are the most characteristic feature of the syndrome and the key to its diagnosis. The findings of multiple facial trichilemmomas appear to be pathognomonic of the disease. Multiple extracutaneous hamartomas are a regular feature of Cowden's disease. The most important hamartomas to recognize include fibrocystic disease of the breast, thyroid goiters or adenomas, multiple polyposis of the gastrointestinal tract, and ovarian cysts. Although many developmental anomalies have been described in these patients, only adenoid facies and high-arched palates appear significant from a statistical standpoint. The most important feature of Cowden's disease, that which makes early recognition absolutely essential, is an increased prevalence of malignant neoplasia primarily in affected female patients, and principally involving the breasts and thyroid gland. All patients, however, must be screened for occult malignancies of all types. A detailed review of the English literature offers a basis for the formation of guidelines that should be helpful in making a diagnosis of the disease.