Traditionally, programs for NC machine tools have been created using either a maunual method or a computer-assisted method. However, both methods are known to be complex, time-consuming and error-prone. This paper presents an intelligent system, called "INPPC" which is interfaced with a CAD system to generate APT NC part program automatically. The INPPC is developed by using VP-Expert rule-based expert system development tool, and obtains the information about the part shape by searching the CAD database, about the process by asking the related questions to the user, and about the machine tooling by searching the tool database. The INPPC is implemented on an IBM compatible PC/AT under MS-DOS, and its performance is demonstrated by consulting a simple example problem.