A dilatant composition comprises (A) an o/w emulsion comprising an ionic surfactant, a water phase, and an oil phase which comprises a ceramide or a linear or branched, saturated or unsaturated C₁₂-C₃₂ fatty acid, wherein the oil phase is in a form of oil droplets having an average droplet size of from 0.01 to 0.2 m; and (B) a nonionic, water-soluble polymer having an average molecular weight of at least 300,000. The dilatant composition according to the present invention is excellent in dilatancy that its viscosity is low when left over standstill but increases abruptly when an external force of a certain intensity or higher is applied, and is useful in a wide variety of fields, e.g., cosmetic preparations such as humectants and massaging aids, shock absorbing agents and materials applied to around automotive crankcases.