In this Letter we suggest an iterative imaging technique based on a simulated annealing (SA) algorithm for a perfectly conducting cylinder. It is numerically shown that an imaging technique that uses SA does not require prior knowledge regarding the center and the shape of an object, whereas one that uses conventional gradient algorithms does require this knowledge regarding a scatterer. It is also shown via numerical simulations that this technique is very insensitive to noise in the scattered field and is not much affected by the observation locations. (C) 1996 John Wiley & Sons, Inc.