Abstract. Using variational arguments we study the non-existence and multiplicity of non-negative solutions for a class equations of the formwhere is a bounded domain in ޒ N , N 3, f is a sign-changing Carathéodory function on × [0, +∞) and λ is a positive parameter.2002 Mathematics Subject Classification. 35J20, 35J60, 35J65, 58E05.