Although serpentinized peridotite may compose a significant proportion of slow-spreading lithosphere, extending up to the seafloor, regional geophysical surveys show a systematic alternation of normally and reversely magnetized seafloor correlated with crustal age, just as in fast-spreading volcanic Pacific crust. Although we did not focus on this problem during Leg 209, we obtained substantial data on the magnetic properties of serpentinized peridotite, which will aid in interpretation of magnetic data for crust formed at slow-spreading ridges.