Tribute to Dr Milton Diamond: Twin Studies of Transsexuality/Twin Research Reviews: Loss of a Twin Brother (Recent Memoir); Oxytocin Adminstration During Twin Delivery; Models of Monochorionic Twinning; Twins' Brain Responses to Watching Films/Human Interest: Oldest Conjoined Twins Pass Away; Twins Discordant for Child Abuse; Twins Married to Twins; Rare Quadruplet Set Delivered; Questions of Coincidence; Reared-Apart Twin Valedictorians.

A tribute to the life and career of Dr Milton Diamond, a leading figure in twin studies of transsexuality and gender identity, is presented. Dr Diamond is famous for revealing the truth about the unsuccessful effort to change a monozygotic male Canadian twin into a female, following accidental ablation of his penis during circumcision. A short summary of recent twin research on human sexuality and transsexuality, focused on Dr Diamond's contributions, is then presented. The tribute and overview are followed by research reviews involving the loss of a twin brother; oxytocin adminstration during twin delivery; models of monochorionic twinning; and twins' brain responses to watching films. The final section of this article covers topics of human interest, including the passing of the world's oldest conjoined twins; twins discordant for child abuse; twins married to twins; the delivery of a rare quadruplet set; questions of coincidence; and reared-apart twin valedictorians.