The structures adduced for α- and β-codeimethine by earlier workers have been confirmed and an alternative structure tentatively advanced for the α-isomer by Robinson disproved. A new α-dihydrocodeimethine has been prepared by the reduction of codeine methiodide and of α-codeimethine with sodium and liquid ammonia, reactions that also involve the production of a compound belonging to the deoxycodeine series. A new type of nitrogen-free substance has been prepared by the degradation of neopine dihydromethine.