The effects of temperature on conventional motor and sensory nerve conduction parameters were studied in normals and in some pathological conditions. Surface stimulating and recording electrodes were used to examine the function of the median nerve. The motor and sensory conduction velocities, the parameters of compound muscle action and sensory nerve potentials were correlated with skin temperature. In the control subjects all nerve conduction parameters changed with temperature. These findings were similar to those published previously, but the mean slope for MCV was lower than that reported in the literature. The amplitude values widely scattered as a consequence of methodological factors, which may mask effects of temperature. Only minor differences were revealed between control subjects and patients. The effect of temperature proved to be similar in the patients and in the normal controls. Therefore, the correction factors determined in normals may be acceptable for abnormal nerves in standardising the measured values with respect to temperature. However, in pathological cases, above all in diabetes mellitus, the slightly reduced changes of conduction velocities vs. temperature may be the source of false negative results in borderline cases when using the normal correction factors. The combination of preserved temperature dependence but decreased conduction velocities may indicate that demyelination and temperature influence the conduction velocities via different mechanisms.