Increasing demands on precision machining have necessitated that the tool move not only with a position error as small as possible, but also with smoothly varying feed rates. In this paper, a 3-axis PC-NC milling system, which is capable of synchronized simultaneous 3-dimensional (3D) machining, is developed. To achieve the synchronous 3D linear and circular motions, new interpolation algorithms based on the intersection criteria are presented. A real-time reference-pulse 3D linear and circular interpolator is developed using a PC to implement in the framework of the PC-NC milling machine reconfigured in this research. The performance test via computer simulation and actual machining have shown that the developed PC-NC milling system is useful for the machining of arbitrary lines and circles in 3D space. (C) 2001 Published by Elsevier Science Ltd.