Carbon and oxygen isotope analyses have been used to test the provenance of the marble of some Attic sarcophagi in the British Museum collection. Of three believed to be of Pentelic marble, only one has been so confirmed. Analysis of fragmentary sarcophagi of similar workmanship has confirmed their Proconnesian origin. Data from fragments of Sidamara sarcophagi have supplemented observations of technique, finish and dimensions of carved figures and decoration to determine whether the fragments come from the same sarcophagus.