If a flexible filament marked at intervals along its length is struck transversely by a flying projectile, high‐speed photography reveals a shifting of the marks caused by passage of a strain wave, and analysis of these shifts provides data on the strain and average strain velocity in the wave. Tests were performed on strips of lightly vulcanized natural rubber at transverse impact velocities up to 65 m/sec, and the resulting strain‐velocity distributions analyzed for viscoelastic effects. The analysis showed that although creep effects were small in the observation time interval of 1–8 msec after impact, significant creep must have occurred at the point of impact within the first millisecond, and additional significant creep occurs at times greater than 8 msec. The strain‐wave‐front velocity calculated from the quasistatic stress‐strain curve was 35.2 m/sec, but a value of approximately 60 m/sec was observed in the tests. The strain at the wave front, however, tended to attenuate as the wave propagated causing a progressive decrease in the observed value of the strain‐wave‐front velocity.