Two galactic length-scale modifications of the Newtonian gravity law are examined in the light of observational dynamical properties of spiral galaxies: (1) the introduction of a Yukawa-type coupling for the gravitational potential, proposed by Sanders (1986); and (2) the introduction of a 1/R correction to the Newtonian gravitational force, proposed by Kuhn and Kruglyak (1987). It was found that the observational evidence is not consistent with the modification proposed by Sanders or with that proposed by Kuhn and Kruglyak.
