I am new to PETSc, so I don't really know how it works. I added this line to my makefile: include $(PETSC_DIR)/bmake/common/base but I had a target named 'clean' defined. Now, when I run my makefile it says: ... ignoring old commands for target 'clean' Does PETSc also define a target named 'clean'? If yes, what does it do? Billy.