Repeated intrathecal injections were given through catheters which had been chronically implanted in the subarachnoid space of rats. Injections were made of cocaine 0.25%, 0.125% and 0.0625%; bupivacaine 0.5%; lignocaine 2% and 0.5%; adrenaline 0.01% (1 in 10 000) and 0.002% (1 in 200 000); and sodium chloride 0.9%. Five injections of 35 microliter of each concentration of each drug were given hourly each day for two days to three rats. No clinical nerve damage was detectable in any rat. The only pathological change found in any rat was the development of cytoplasmic vacuolation in the neurones of the anterior and posterior horns. The changes were most prominent after injection of 0.9% sodium chloride and bupivacaine, whilst lignocaine (0.5 and 2%) showed the least number of vacuoles, which were also the smallest in size. Adrenaline and cocaine were intermediate in effect. There was no evidence of cell death. These changes were not seen in control animals in which catheters had been implanted but no injections had been given. The changes were mild and it is concluded that the agents tested caused no significant damage.