O-17 NMR longitudinal and transverse relaxation rates and chemical shifts have been measured for aqueous solutions of the chelate complex [Gd(DTPA BMA)(H2O)] at variable temperature, pressure, and magnetic field. The results were analyzed in terms of the water-exchange kinetics, the rotational motion of the chelate complex, and the electronic relaxation of the Gd3+ ion in the chelate complex. The water-exchange kinetic parameters are k(ex)298 = (4.3 +/- 0.2) X 10(5) s-1, DELTAH(double dagger) = 46.6 +/- 1.3 kJ mol-1, DELTAS(double dagger) = +18.9 +/- 4.0 J K-1 mol-1, and DELTAV0double dagger = +7.3 +/- 0.2 cm3 mol-1. These results indicate a limiting dissociative, D, mechanism, in common with other Gd3+ chelate complexes with one inner sphere water molecule. The rotational motion of the complex is governed by a correlation time tau(c)298 = (1.67 +/- 0.05) X 10(-10) s with activation energy E(c) = 21.6 +/- 0.1 kJ mol-1. The magnetic field dependence of the longitudinal electronic relaxation rate can be described by a zero-field splitting interaction, modulated by a correlation time tau(v)298 = (3.4 +/- 0.8) X 10(-11) s with activation energy E(v) = 9 +/- 2 kJ mol-1. Comparison of this correlation time with the rotational correlation time indicates that the zero-field splitting is produced by fluctuating distortions of the chelate complex. It was necessary to assume a second, field-independent, electronic relaxation mechanism, which we ascribe to spin rotation. The effect of the above parameters on the proton relaxivity, and hence the efficacy as a magnetic resonance imaging contrast agent, of [Gd(DTPA-BMA)(H2O)] OMNISCAN injection is discussed.