Crystals of barium titanate (BaTiO3), with linear dimensions up to ˜ 2 mm., have been produced from solutions in carbonates and chlorides, and (when pure) are hard, clear, pale yellow in colour, and of cubic external symmetry. We are greatly indebted to Prof. P. Scherrer, Zurich, for advice on methods of producing these crystals. The results of optical and X-ray examination of the crystals are summarized below.