Automotive applications of millimeter wave radar systems are gradually spreading into the market in Japan, US and Europe because of the high performance under adverse weather conditions. They are adaptive cruise control (ACC), pre-crash safety and collision warning systems. To manage multiple vehicles properly, FM-CW (Frequency Modulated Continuous Wave), multiple frequency CW with monopulse and doppler principles and FM pulse doppler methods are used in the systems. The late improvement of the linearity and cost of the voltage controlled oscillator encourages the use of FM-CW and makes it the most popular method in an automotive market. FM-CW is an effective method for objects with low relative velocity, but has in principle the ambiguity on the separation of the range/distance and velocity for a single object with wide relative velocity range and the identification of the correct combination of beat frequencies for multiple objects. In this paper a new practical algorithm is proposed for multiple object detection in automotive FM-CW radars. This algorithm can provide the distance and relative velocity of objects without the ambiguity of distance and relative velocity. Since it is simple, straight-forward and fast, it is suitable for automotive application, in which the update time is less than 100 ms. This algorithm is based on two down chirp frequency sweeps with small slope-difference. Since the difference is small, the correct pairs of beat frequencies can be identified automatically. Because of the down chirps, the polarity of beat frequencies owing to the distance and the doppler becomes the same for an approaching object and then the distance and the velocity are uniquely determined. Namely the distance and velocity information for multiple objects can be calculated without the ambiguity in a simple manner.