Conductometric investigation of n-tetrabutylammonium hexafluorophosphate (NBu4PF6) was performed in methanol (MeOH), ethanol (EtOH), 2-propanol (2-PrOH), acetone (ACE), 3-pentanone (PEN), tetrahydrofurane (THF), dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), dichloromethane (DCM). acetonitrile (ACN) and N-methylformamide (NMF) at 298.15 K. The limiting molar conductivities (A(o)) and the association constants (K-A) were derived from the Lee-Wheaton conductivity equation. The limiting ion conductivities (lambda(o)(+/-)) were evaluated using n-tetrabutylammonium tetraphenylborate (NBu4BPh4) as a "reference" electrolyte according to the method of Krumgalz. The Stokes' radii (r(st)) of PF6- anion were estimated and used for the calculation of its solvation numbers (S-n.) in investigated solvent media. The mobility of ions was found to be completely controlled by the bulk viscosity (eta) and consequently the Walden product (W=eta A(o)) was found to be almost constant. Slight ionic association was found for NBu4PF6 in solvent media with dielectric constant epsilon > 16 while the association becomes more significant in THF which has the lowest dielectric constant (epsilon = 7.5). The S-n values indicate weak interactions between PF6- and solvent molecules. The only exception was found in the case of MeOH, in which the great S-n value can be attributed to a hydrogen bond formation between the fluor atoms of PF6- and hydrogen of MeOH molecules. (c) 2008 Elsevier B.V. All rights reserved.