Crystallographic properties of the spinel systems Li0.5Ga2.5−xMnxO4(0≤x≤0.7), Li0.5Fe2.5−xMnxO4(0≤x≤0.5), and Li0.5Al2.5−xMnxO4(0≤x≤0.5) have been investigated in order to determine the effects of trivalent manganese substitution on the crystal chemistry of the ordered spinel hosts. In each system relatively small concentrations of Mn3+removed long‐range ordering of lithium ions on the octahedral sites. This loss of order was accompanied by anomalies in the dependence of lattice parameters on composition. These observations can be qualitatively interpreted by assuming that Mn3+ions tend to cluster in order to reduce the elastic energies associated with Jahn‐Teller stabilization. These effects may provide indirect evidence for lattice imperfections such as have been invoked to account for squareB‐Hhysteresis loops in ferrite materials containing Jahn‐Teller ions.