Since the 1990s there has been an increase of 172 per cent of people diagnosed as autistic. ‘A huge increase in cases’ looks at the possible causes of autism. It is very unlikely that autism is caused by some adverse environmental event after birth, although the personal experience of many parents goes against this. Vaccination always has an aura of suspicion, however the introduction of the MMR, the triple vaccination, did not go together with a steep rise in cases. The increase is not a mystery or a sign of an epidemic. It can be explained by broadening diagnostic criteria and increased awareness.