Pertussis vaccine was originally accused of provoking a short latency explosive encephalopathy with serious mental and physical consequences. Reports of recurrence of encephalopathy, worse after each dose, strengthened the notion of causality. Anecdotal associations can be no more than hypothesis-generating. With no distinctive clinical or pathological neurology, a major epidemiological study was necessary to answer the question "Does whooping cough vaccine cause brain damage in children"? The British national Childhood Encephalopathy Study (NCES) seemed to indicate that very rarely the answer was yes. Unfortunately the NCES confused disorders which might be notified as "encephalopathy" with actual brain damaging events, imaging a continuum of injury. Close scrutiny of the individual cases, as was possible during the recent test case in the High Court of London, shows that all the temporally associated cases with permanent sequelae had either viral encephalitis or Reye's syndrome. No cases were unexplained. There was an apparent excess of febrile convulsions in the first 24 hours, but all these children were normal at follow-up. The short latency explosive encephalopathy with adverse outcome predicted by the earlier case series did not occur. The NCES gives no support to the idea that pertussis vaccine damages children's brains. Contra-indications to DTP should be the same as to DT.