Autism has been the subject of intense public and professional attention in recent years. One of the biggest questions is what causes it. Like the discoveries made about schizophrenia in the late 20th century, we are learning that autism too has genetic and environmental determinants. Here Dr Daphne Keen discusses her paper which attempts to answer the question of whether maternal immigration and ethnicity, together or in tandem, are implicated as being risk factors in young children who develop autism.