For a fixed rational number g ∈ {−1, 0, 1} and integers a and d we consider the set N g (a, d) of primes p for which the order of g(mod p) is congruent to a(mod d). It is shown, assuming the Generalized Riemann Hypothesis (GRH), that this set has a natural density δ g (a, d). Moreover, δ g (a, d) is computed in terms of degrees of certain Kummer extensions. Several properties of δ g (a, d) are established in case d is a power of an odd prime.