We observed the retention loss phenomena of the nanodomains with an average diameter of 36 nm and that of the square domains with a size of 1 and 25 mu m(2) that were reversed by an applying electric field at an atomic force microscopy conductive tip in a heteroepitaxial PbTiO3 thin film, which was fabricated via hydrothermal epitaxy below Curie temperature, T-C. While the nanodomains did not undergo significant retention loss until 5.3x10(6) s, the square domains revealed some retention loss for a fixed period after long latent periods. The observed phenomena were explained in terms of the instability of the curved c/c domain wall and the compressive strain energy. Analyses showed that the nanodomains composed a cylinder extending to the bottom electrode; however, the square domains had a curved c/c domain wall, including the compressive strain energy, and these factors caused the retention loss. (c) 2006 American Institute of Physics.