Currently the default visibility is hard-coded in the compiler, but for some projects/teams changing the default visibility for one or more kind of member can be desirable. Boo should allow this to be set (by a macro for instance) through CompilerParameters properties : DefaultTypeVisibility DefaultMethodVisibility DefaultPropertyVisibility DefaultEventVisibility DefaultFieldVisibility Additionally the setting can be changed through define symbols such as DEFAULT_TYPE_VISIBILITY and so on for each kind of member.