In this note, there are determined all biscalars of a system of s ≤ n linearly independent contravariant vectors in n-dimensional pseudo-Euclidean geometry of index one. The problem is resolved by finding a general solution of the functional equation F(Au1 , Au2 , . . . , Aus ) = (sign(det A))F(u1 , u2 ,...,us ) for an arbitrary pseudo-orthogonal matrix A of index one and the given vectors u1 , u2 ,...,us .