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It is found that the electron-paramagnetic-resonance ͑EPR͒ spectrum of the ͓Ni͑H 2 O͒ 6 ͔ 2ϩ complex diluted in crystal of zinc fluoborate ͑1.5 at. %͒, as obtained with the magnetic field along the distortion axis of the crystal field with trigonal symmetry, at a temperature of 77 K and using a X-band spectrometer, exhibits some satellite lines close to the expected two main lines. These lines were explained to be due to magnetically coupled pairs between nearest neighbors. The explicit account of dipolar and isotropic exchange interactions was introduced in the spin Hamiltonian of the pairs and the exact eigenvalues have been calculated. The dipolar and exchangeinteraction parameters have been determined directly from the line positions, respectively, as uϭ98Ϯ3 G and JϭϪ194Ϯ13 G ͑ferromagnetic͒. This result indicates that the dipolar interaction generally excluded in the magnetic interaction study of ͓Ni͑H 2 O͒ 6 ͔ 2ϩ complex is not negligible. The quantitative determination of these magnetic interactions in this way was made possible by a combination of EPR and magnetic dilution techniques.

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