The preparation of two new mixed-valence compounds, CaMn 3O 6 and CaMn 4O 8, are described and their magntic and EPR behavior investigated. The Mn moments in both compounds have nearly spinonly values. CaMn 3O 6 and CaMn 4O 8 order ferrimagnetically near 3 and 89 K, respectively. The broad, Lorentzian EPR lines indicate a significant exchange interaction between Mn 3+ and Mn 4+ ions. The magnetic and EPR results suggest a strong ferromagnetic interaction between Mn 3+ and Mn 4+ ions and a comparable antiferromagnetic Mn 3+Mn 3+ and/or Mn +Mn 4+ interaction.