The response properties of feline cold receptors were analyzed under control conditions, during conditions of altered external calcium concentrations and during application of menthol, catecholamines and ouabain. Afferent activity was extracellularly recorded from cold fibres of an isolated preparation of the tongue. Reduced calcium levels (0.5 mM) generally enhanced and elevated calcium levels (5.0 mM) suppressed cold fibre activity. The effects of menthol (105 M) on cold receptors were qualitatively similar to those of reduced calcium. Application of adrenaline and noradrenaline (10-6 M) were predominantly inhibiting. In cold receptors, the mean discharge rate is determined by the frequency of an oscillating receptor process and the probability of each cycle of this process to initiate afferent impulses. All measures mainly affected the probability of impulse generation rather than the oscillation frequency. Application of ouabain (1(F6 M) resulted in excitatory responses, caused by an increase of both probability of impulse generation and frequency of the oscillating receptor process. It is concluded that cold receptor function is based on a specific combination of common neuronal elements rather than on specific sensory processes.