Ferroelectric compounds in the family have been prepared as ceramics and single crystals. The solid solution limit increases with ionic radius: exceeds 2 for La3+ and Pr3+ and approaches zero for the smaller Yb3+ and Lu3+ ions. The larger rare earth ions also stabilize the paraelectric phase. The dielectric properties and crystal chemistry of the bismuth titanates are discussed with reference to related structures, and the results of preliminary optical and electrical measurements are given.