[Author] A. A. Arkhipova [Title] New a priori estimates for nondiagonal strongly nonlinear parabolic systems [AMS Subj-class] 35K45 Initial value problems for parabolic systems 35K50 Boundary value problems for parabolic systems 35K55 Nonlinear PDE of parabolic type 35B65 Smoothness and regularity of solutions of PDE 35A20 Analytic methods, singularities [Abstract] We consider elliptic and parabolic systems of equations with quadratic nonlinearities in the gradient. We discuss new description of regular points of solutions of such type systems. For a class of strongly nonlinear parabolic systems, we estimate locally the Holder norm of a solution. Instead of smallness of the osscillation, we assume local smallness of the Campanato seminorm of the solution under consideration. Theorems about quasireverse Holder inequalities proved by the author are essentially used. We study systems under the Dirichlet boundary condition and estimate the Holder norm of a solution up to the boundary (up to the parabolic boundary of the prescribed cylinder in the parabolic case). [Keywords] parabolic systems, strong nonlinearity, regularity [Comments] English, LaTeX, 25 pp. [Contact e-mail] arina@AA1101.spb.edu