Whole-cell suspensions of Cylindrocarpon didymum were observed to transform 2,2'-bimorphine to the compounds 10-alpha-S-monohydroxy-2,2'-bimorphine and 10,10'-alpha,alpha'-S,S'-dihydroxy-2,2'-bimorphine. Mass spectrometry and (1)H nuclear magnetic resonance spectroscopy confirmed the identities of these new morphine alkaloids.