In a frequency-modulation system, a sudden jump in carrier frequency corresponding to a Heaviside unit signal will result in a transient depending on the receiving-filter bandwidth. If this bandwith exceeds twice the maximum frequency swing, the shape and duration of the transient is shown to be about the same as in an amplitude-modulation system with the same bandwidth; for narrower filters the transient lasts longer. These results are applied to several practical cases. The transient is favorably affected by using an amplitude limiter and by arranging the filter pass band so as to enclose the maximum frequency swing symmetrically.