Many dynamic processes in Liquids fall into the rotational motion regime with correlation times of 10(-11) to 10(-12) s, which are difficult to probe by conventional electron paramagnetic resonance (EPR) spectroscopy (8.8-9.5 GHz, X-band). At 95 GHz (W-band), the range of rotational correlation times (tau(R)) measured by EPR for the typical nitroxide radicals is extended by a factor of 7 toward short times, producing more pronounced motional effects on the line width at the same tau(R). However, for protonated nitroxide spin probes, the inhomogeneous broadening caused by proton superhyperfine (shf) interactions still contributes significantly to motionally narrowed 95 GHz spectra, and this makes direct estimation of tau(R) inaccurate. A multifrequency approach to solve this problem is reported. Information on proton hyperfine interactions can be obtained from X-band spectra. This significantly improves the accuracy of T-2(-1) determination from W-band data without additional NMR or ENDOR experiments. The utility of this approach is demonstrated by two examples of nitroxide probes with complex superhyperfine structure : (i) 3-doxyl-17 beta-hydroxy-5 alpha-androstane (probe #1) and (ii) 3-maleimido-PROXYL (probe #2). EPR spectra of these probes at both X- and W-bands were studied. X-band EPR spectra from probe #1 revealed a well-resolved proton hyperfine structure; hyperfine coupling constants were determined by least-squares computer simulation. : (i) 3-doxyl-17 beta-hydroxy-5 alpha-androstane (probe #1) and (ii) 3-maleimido-PROXYL (probe #2). EPR spectra of these probes at both X- and W-bands were studied. X-band EPR spectra from probe #1 revealed a well-resolved proton hyperfine structure; hyperfine coupling constants were determined by least-squares computer simulation.