An efficient reductive conversion of 3-iodomethylcephalosporin and 3- acetoxymethylcephalosporin derivatives mediated by indium into the corresponding 3- methylcephems and 3-methylenecephams in moderate to good yields has been developed in an aqueous system. 3-Methylenecephams are converted into the corresponding 3- methylcephems under previously reported basic conditions quantitatively.