Manslaughter continues to be difficult to define and apply, so much so that in two recent decisions the Court of Appeal demanded that the state of involuntary manslaughter be reviewed and reforms be suggested. The greatest conceptual difficulties concerning this offence relate to ascertaining what its ambit actually is and how wide it should be. For the most serious kinds of homicide the crucial distinction concerns where the boundary between murder and manslaughter should be drawn. After much confusion, murder now requires proof of an intention either to kill or to cause serious injury. Much more difficulty arises in identifying the boundary between manslaughter and mere accident. This raises complex issues as to the relationship between criminal and civil liability.