Steve,

SetFocus is working fine. Check the sequence of events in your code;

If nKeyCode = 13 && Enter key
* Hit enter key
thisform.lstinfo.additem(this.value)
* Item added to list
this.value = ""
* value blanked out
this.setfocus()
* Focus set to this control
endif
* Keypress ends and VFP processes the Enter key
* Default for enter key is to move focus to the next control

As Bruce told you you need to stop the default processing of the enter key.