Electronic Journal of Differential Equations, Vol. 2002(2002), No. 53, pp. 1-17. Title: Uniqueness theorem for $p$-biharmonic equations Author: Jiri Benedikt (Univ. of West Bohemia, Czech Republic) Abstract: The goal of this paper is to prove existence and uniqueness of a solution of the initial value problem for the equation $$ (|u''|^{p-2}u'')''=\lambda |u|^{q-2}u $$ where $\lambda\in{\mathbb{R}}$ and $p,q>1$. We prove the existence for $p\geq q$ only, and give a counterexample which shows that for $pq$ the uniqueness does not hold true (we give a corresponding counterexample again). Moreover, we deal with continuous dependence of the solution on the initial conditions and parameters. Submitted April 15, 2002. Published June 10, 2002. Math Subject Classifications: 34A12, 34C11, 34L30. Key Words: p-biharmonic operator; existence and uniqueness of solution; continuous dependence on initial conditions; jumping nonlinearity.