EPR spectra at 94.5 GHz (3 mm) and 249.9 GHz (1 mm) have been measured for the dichloro-, dibromo-, and diiodobis(triphenylphosphine oxide)manganese(II) complexes. These compounds have a distorted tetrahedral geometry, and the highest possible symmetry obtainable is Cr,. Because the spectra are taken in the high-field limit, they are simple and much easier to interpret than at lower magnetic fields. Accurate values of the zero-field splitting parameters, D and eta (E/D), are determined by least-squares fitting and homotopy using matrix diagonalization. The compounds have g-values near 2 and large values of D and eta. Across the series, D increases from 0.165 to 0.906 cm(-1), while eta decreases slightly from 0.273 to 0.246.