The surface free energy components of calcium carbonate for bare and surfactant-treated surfaces were studied by the thin-layer wicking technique. The surface precoverage from a 10(-3) M aqueous solution of cetyltrimethylammonium bromide (CTMABr) and sodium dodecyl sulfate (SDS) caused a decrease in the electron donor component and an increase in the electron acceptor component. The changes were more pronounced in the case of CTMABr than for SDS. Consequently, in the presence of the cationic surfactant, the surface becomes hydrophobic while the SDS-precovered surface is still slightly hydrophilic. The presence of a radiofrequency (RF) electric field (44 MHz, 60 V peak-to-peak no-load amplitude) during wicking experiments perpendicularly to the wicking direction also decreases the electron donor component and increases the electron acceptor component. The increase is relatively higher for the surfactant-precovered surfaces. The RF treatment does not change the hydrophobicity of the bare surface but changes the hydrophobic CTMABr-precovered surface to slightly hydrophilic. On the contrary, the slightly hydrophilic SDS-preadsorbed surface becomes slightly hydrophobic in the presence of RE It is concluded that the free energy changes appearing in the presence of RF are due to reorientation of the adsorbed surfactant molecules and/or changes in the structure of the water molecules hydrating the surface.