The results of neutron-diffraction measurements are reported which confirm that superconducting TmRh4B4 orders magnetically at TM0.7 K. The modulated antiferromagnetic structure deduced from the data is of particular interest, considering the similarity of certain other physical properties of TmRh4B4 to those of the ferromagnetic, reentrant superconductor ErRh4B4. © 1983 The American Physical Society.