A medical implant made of metal is claimed where the metal is degradable in vivo by corrosion. - Preferably the metal is an alloy whose main component is an alkali(ne earth) metal, Fe, Zn or Al, especially Mg, Fe or Zn, and whose subsidiary component is Mn, Co, Ni, Cr, Cu, Cd, Pb, Sn, Th, Zr, Ag, Au, Pd, Pt, Si, Ca, Li, Al, Zn and/or Fe. The alloys especially comprise (a) 50-98 (preferably 55-65)% Mg, 0-40 (preferably 30-40)% Li and 0-5% other metals (b) 88-99% Fe, 0.1-4% Cr, 0.1-3.5% Ni and up to 5% other metals or (c) 90-96% Fe, 3-6% Cr, 1-3% Ni and 0-5% other metals.