The problem of optimal actuator number and placement for the vibration control of large flexible space structures is addressed in this work. The inherent mass of the actuators is integrated in the number and placement algorithm. The algorithm utilizes concepts from genetic programming, which is loosely based on Darwin’s “survival of the fittest” theories. The paper develops the genetic algorithm in the context of the actuator number and placement problem. Examples are presented which demonstrate the genetic algorithm and the effect of actuator mass on the placement and number problem.