Abstract
A one-dimensional theory of tachyons, which is noninvariant under space inversion and is based on extending the Lorentz transformations to inertial co-ordinate systems having relative velocities greater than that of light, is given. It is shown that the theory is fully causal and exhibits a reciprocity between tachyons and bradyons according to which a tachyon with dimensionless velocity v/c>1 behaves as a bradyon with dimensionless velocity c/v<1 and with the space and time components of its "two-vectors" interchanged.