The transposition and excision rates of the 412 retrotransposable element were estimated in five populations of Drosophila simulans differing in their average 412 copy numbers, which ranged from 2 to 54. The transposition rate was found to equal 1 x 10(-3) to 2 x 10(-3), independently of copy number. No excision was detected. These values eliminate autoregulation as a force maintaining copy number of the 412 element in natural populations of D. simulans.