Structure, growth and morphology of various inorganic salts (CaCl2, K2CO3 and CaCO3) was investigated when crystallized in a polyethylene oxide (PEO) matrix. The PEO has profound influence on the crystalline phase and morphology of these salts which crystallize out when added in excess of 2:1 molar ratio. PEO-CaCl2 crystallizes in orthorhombic configuration with a = 8.2 A ̊, b = 13.5 A ̊ and c = 19.26 A ̊, while PEO-K2CO3 has lattice parameters of a = 7.46 A ̊, b = 5.45 A ̊ and c = 7.64 A ̊ with preferential orientation of crystallites. CaCO3 formed "in situ" from these matrices shows a mixed phase of vaterite and monoclinic forms and grows with preferential row nucleation along the polymeric fibres. © 1993.