A composition dependent semiconductor-metal transition is observed in a new series of Ti oxides of the type LnBa 2 Ti 3 Oy (Ln = La, Gd and Y) in which Ti is in lower and/or mixed valent state. The new phases have been synthesised by the de are melting technique and characterised by powder X-ray diffraction, thermal analysis, electrical and magnetic measurements. Single phase compounds are found to form only when the nominal (average) Ti valence (V T i ) is between 3.67 to 2.33. The crystal structure is simple cubic in which Ln/Ba and various Ti ions occupy respectively the A- and B-sites of a disordered ABO 3 perovskite type lattice. The semiconductor metal transition is also found to depend on the V T i The compounds show semiconducting behaviour for 3.67 < V T i > 2.67 and are metallic when V T i = 2.33 which is the lowest possible value of V T i in the system. No evidence for superconductivity has been observed in any of the metallic compositions down to 15 K.