A coordination polymer [Co(hfac)(2)center dot L] (L = o-ethoxyphenyl nitronyl nitroxide) was prepared, structurally characterized, and revealed to show a record coercive field of 54 kOe at 6 K. The magnetic easy axis was found to be perpendicular to the chain direction. Interchain dipolar coupling is important for the bulk and/or single-chain properties in this series.