This paper is concerned with the English Court of Appeal's decision in Yearworth v North Bristol NHS Trust that six men had, for the purposes of their claims against the trust, ownership of the sperm they had produced. The case has been discussed by many commentators and most, if not all, of those who have discussed the case have claimed or assumed that the court held that the claimants had property rights in the sperm they had produced. In this paper, (...) I advance an interpretation of the case that does not regard the court as deciding that the men had property rights in the sperm they had produced. On this view, the ‘ownership’ that the Court of Appeal purported to vest in each of the men was not a right in rem, a right ‘binding the world’. If this is so, it is perhaps unsurprising that some scholars, evaluating the success of the court's reasoning as a justification for vesting the claimants with property rights, have found it to be unsatisfactory. (shrink)