I'm trying to use KSoap2 library. I put the file Ksoap2-android-assembly-2.5.7-jar-with-dependencies.jar in the directory workspace myproject libs Then I setted it in build path. (libraries) I have error just when I run the application: 11-27 10:32:56.260: E/dalvikvm(1593): Could not find class 'org.ksoap2.serialization.SoapObject', referenced from method associated to this code line: SoapObject request = new SoapObject(NAMESPACE, METHOD_NAME); I tried also with the steps suggested in this thread exception while using ksoap2 library for android whitout success