The first ambulatory clinic for the prevention of women's cancers was the Strang clinic of New York City, founded by L'Esperance in 1932. Careful and complete clinical examination and some additional tests were the basis for the initial diagnosis of early cancers. In 1945, the Papanicolaou test was added as a new examination tool. Some years later, the Strang clinic proved that detection and treatment of cervical cancers in their preinvasive phase were an important factor for the control of this frequent and mortal neoplasia. The Strang clinic demonstrated that the preventive medicine principles can be applied on the discovery and diagnosis of initial cancer cases and that the treatment applied in such cases offers the best results. Additionally, according with these results, the early diagnosis and treatment of cancers should be the work's philosophy applied in all the health systems.