Doubt remains as to whether the increased risk of suicide in monozygotic twins is a response to the intense grief over the loss of a close relative, or whether a common genotype is associated with suicidal behaviour. A number of researchers have reported greater suicide ideation among bereaved monozygotic twins as compared to dyzygotic twins, suggesting that a loss due to suicide may increase the risk of suicidal behaviour in the surviving co-twin. The aim of the present article is to address the issue of the intense grief experienced by twins after the co-twin suicide. (25 refs.)