The existing SPLP method for the determination of therncomplex dielectric permittivity and the thickness of metalrnfilm .1.s reviewed. A close electrodynamic analysis ofrnSPLP dispersion properties in very. thin metal films isrnmade. The analysis is based on the numerical solution ofrnthe exact dispersion equation using the 'Downhill' methodrnand subsequent selection of physically reasonable results.rnThe selection is performed via the comparison of the powerrnflows through the boundaries of the metal film in therntransverse direction.rnThe explicit expressions for the components of thernpower flo~1 in the Kretschmann Prism-Metal Film-Airrnconfiguration have been derived.rnAnalysis made shovled that splitting of the classicalrndispersion equation into two branches (w - mode and w+ mode)rnknown in li~erature for the case of symmetriC environmentrnoccurs also for the case of asymmetric environment, butrnthe 0/ mode branch is represented by a number of discreternpoints only. It vias also shown that part of the IJj + modernbranch known in 11 terature is physically unreal.rnIn addition to the two branches mentioned a thirdrn'side' branch have been found, which turned out to bernphysically unreal.rnThe study of physically significant results revealedrnback-bending segments in the w- and w+ branches whichrndemonstrate the phenomena of artificial anomalous dispersion The developed teclli1ique of the numerical solutionrnof the exact dispersion equation allo~lS to extehdrnapplicability of the SPLP method to the case of very thinrnmetal films and puts no restrictions on the type of thernenvironment