Direct measurements of rotational correlation times of luminescent ruthenium(II) probes (RuL(3)(2+), RuL(2)L(2+) and RuL(2)(CN)(2), L and L’ = alpha-diimine) by differential polarization phase fluorimetry have been made. Correlation times and limiting anisotropies are related to structural parameters of the complexes. Implications for the use and design of metal complexes as dynamic probes of motions of macromolecular systems such as organic and biopolymers are given.