Fine gold particles grown on the electrode in various acid solutions at different electrode potentials have been studied by means of transmission electron microscopy. It was found that the octahedral f.c.c. single crystal particles are grown at positive electrode potentials (SCE), but the pentagonal decahedron and hexagonal icosahedron particles are grown preferentially at negative electrode potentials (SCE). Different shapes and structures of gold particles formed at different electrode potentials are attributed to the surface energy of the growing particles, which may be influenced by the electrode potential. The (1 x 1) structure may correspond to lower surface energy structure at positive electrode potentials, but the surface at negative electrode potentials prefers to take the hexagonal arrangement of the atoms to lower the surface energy. Anions showed different influences on the growth of particles, so the effect of anions is discussed in this paper.