Because of a renewed interest in British portrait miniatures, there is a growing demand for their proper conservation. Many miniatures are in poor condition, some are virtually irrecoverable. This discussion covers general principles of current treatment applied to correct the structural deterioration of portrait miniatures painted with watercolor on parchment and ivory. The problems are examined in terms of the specific materials, support construction methods, and painting techniques employed by their creators at successive stages in the technical and stylistic development of the art, i.e., ca. 1525 to ca. 1710, ca. 1710 to ca. 1740, ca. 1740 to ca. 1830, and ca. 1830 to ca. 1850.