Electronic Journal of Differential Equations, Vol. 2003(2003), No. 59, pp. 1-11. Title: Hopf-type estimates for solutions to Hamilton-Jacobi equations with concave-convex initial data Authors: Nguyen Huu Tho (Bureau of Education, Vietnam) Tran Duc Van (Hanoi Institute of Math., Vietnam) Abstract: We consider the Cauchy problem for the Hamilton-Jacobi equations with concave-convex initial data. A Hopf-type formula for global Lipschitz solutions and estimates for viscosity solutions of this problem are obtained using techniques of multifunctions and convex analysis. Submitted July 3, 2002. Published May 21, 2003. Math Subject Classifications: 35A05, 35F20, 35F25. Key Words: Hamilton-Jacobi equations; Hopf-type formula; global Lipschitz solutions; viscosity solutions