25 rapidly adapting mechanoreceptor afferents were recorded in an in vitro preparation of rat skin and nerve. Single units were recorded while the skin was subjected to dynamic uniaxial stretch using a pseudo Gaussian noise (PGN) input waveform. Force was the controlled variable in stretch stimuli. Measured loads and displacements were used to calculate tensile stresses, strains, and their rates of change. Associations between spike responses and individual stimulus components such as tensile stress or strain were determined in a reverse correlation design, using multiple logistic regression. Spikes were strongly associated with stress, at memory times from 0 to 14 msec, and with the rate of change of stress, at a memory times between 6 and 18 msec. There was a strong interaction between stress and its rate of change, with a maximum value at a memory time of 10 msec. We found no relationship between spike responses and strain.