The Woolley and Roe case. A reassessment. In 1953, two patients, Cecil Roe and Albert Woolley, sued their anaesthetist for alleged negligence because they had developed painful spastic paraparesis after spinal anaesthesia. The court found that phenol, which was used to sterilise the outside of the ampoules of local anaesthetic, had percolated the glass through invisible cracks, contaminating the solution, but that the anaesthetist could not have been aware of this risk. The case was important, despite the fact that judgement was in favour of the anaesthetist, because of the fears that it generated over the incidence of paralysis after spinal anaesthesia. The 'invisible crack' theory has been the subject of much scepticism. New information has been obtained, and the case re-examined objectively. The most probable source of contamination, which led to paralysis in the two patients, and in a third who received spinal anaesthesia on the same day, has been identified. A similar explanation may lie behind a number of other episodes of paralysis associated with spinal anaesthesia. 