The Workshop on Nonlinear Equations is by now a familiar conference among researchers in analytical and topological methods in partial differential equations. Originally a binational agreement between Italy and Brazil, the event now includes speakers of many countries. Previous meetings were held in Bergamo, Como and Verbania, in Italy, and Campinas and Rio de Janeiro, in Brazil. This 9th Workshop is organized by the Universidade Federal da Paraíba, in João Pessoa, Brazil.