Methylmalonyl-CoA epimerase, which specifically interconverts the (2R)- and (2S)- epimers of methylmalonyl-CoA, was purified 95-fold from Propionibacterium shermanii by a new method that affords apparently homogeneous enzyme, in 80-100mg quantities, in yields representing about 40% of the activity in cell-free extracts. The specific activity of the purified enzyme, 10.1 mukat/mg, is much greater than previously reported. Native methylmalonyl-CoA epimerase has Mr about 33000, and apparently consists of two identical subunits. The purified enzyme is stable indefinitely when stored at -20 degrees C and pH 8.5, but contrary to previous reports it is not unusually acid-stable. The activity of methylmalonyl-CoA epimerase is increased by Co2+, and to a smaller extent by Ni2+, Mn2+ and Zn2+.