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In the Winstein-Grunwald relationship for solvolysis reactions, log k¡k0 = mY, Fis a parameter taken to represent "solvent ionizing power" and not the nucleophilicity of the solvent or its ability to promote rate-determining elimination. Using r-butyl chloride, the reference compound chosen by Winstein and Grunwald to evaluate F, it is impossible to rule out these other mechanistic contributions. In order to assess the role of solvent, rate constants for solvolysis of 1-adamantyl bromide in fourteen solvents were determined; data for eight additional solvents were obtained from the literature. In such a bridgehead substrate, backside nucleophilic solvent attack and elimination are both impossible. In general, an excellent correlation between data for r-butyl chloride and 1-adamantyl bromide is found indicating that r-butyl chloride, in most instances, solvolyzes by a limiting mechanism, free from nucleophilic solvent participation and from rate-determining elimination. Significant dispersion is found for aqueous trifluoroethanol solvent systems; this deviation is discussed in terms of specific substrate and leaving group effects. The Winstein-Grunwald relationship for solvolysis reactions, log k/ko = mY, affords a useful although not entirely precise tool for the calculation of solvolysis rates.3 The parameter m is taken to be a measure