With the advance of far-infrared laser applications the need arises to vary the radiation intensity over a large dynamic range. An example is laser radar where a return loss of 50 or even 100 db has to be achieved without distorting the wavefront. First we review the more common techniques used to attenuate FIR laser beams, and then describe a new step attenuator that uses diffracting metal mesh screens to attenuate the laser radiation. Broadband performance over nearly one decade of frequency is achieved. The design can handle even higher peak and average FIR powers than are available at present, while maintaining beam quality in all respects, including arbitrary input polarization.