Conduction has been examined serially through the experimental demyelinating lesion produced by the direct micro-injection of lysophatidyl choline into the cat spinal cord. Conduction was blocked during the phase of demyelination. Remyelination commenced during the latter part of the second week, and conduction through the lesion was restored in some fibres at this time. The refractory period of transmission was initially prolonged. As remyelination proceeded, conduction was restored in increasing numbers of fibres. Within three months the responses were stable and the refractory periods of transmission had returned to normal even though the new internodes were still abnormally thin and were generally shorter than normal. Restoration of conduction by remyelination is likely to contribute to recovery from compressive and traumatic lesions of the central nervous system but probably plays little part in the remissions of multiple sclerosis.