Nanocrystalline　La1.5Ln0.5Ti2O7　(Ln　=　Pr,　Gd,　Er)　solid　solutions　were　prepared　by　a　polymeric　complex　method.　The　samples　were　characterized　by　X-ray　diffraction　(XRD)　analysis,　transmission　electron　microscopy　(TEM),　UV-vis　diffuse　reflectance　spectra　(DRS),　energy　dispersive　X-ray　spectrum　(EDS),　thermogravimetric　analyses　(TGA)　and　differential　thermal　analyses　(DTA).　The　photocatalytic　activity　of　La1.5Ln0.5Ti2O7　(Ln　=　Pr,　Gd,　Er)　was　evaluated　by　the　photocatalytic　degradation　of　methyl　orange　(MO).　La1.5Gd0.5Ti2O7　showed　the　best　photocatalytic　activity　and　it　was　supposed　that　the　half-filled　electronic　configuration　of　Gd3+　can　promote　charge　transfer　and　enhance　the　photocatalytic　activity.　The　difference　in　the　photocatalytic　activity　observed　for　La1.5Ln0.5Ti2O7　(Ln　=　La,　Pr,　Gd,　Er)　can　be　related　to　the　different　Ln　4f　shell.　©　2006　Elsevier　B.V.　All　rights　reserved.