The methods for partition coefficient (Kp) determination were developed for different concentrations of N-(2-hydroxybenzyl)-ω-amino carbonic acids, a new class of amphipathic fatty acid derivatives (An), their deutero (AnD) and bromine (AnBr) derivatives. To do this the following methods were used:2H-NMR, equilibrium dialysis, centrifugation and fluorescence spectroscopy. Kpdependence on the An concentration is discussed. Kpvalues for AnBr were more than 120-times higher than those for An, the differences between them being smaller than those for the corresponding An. This series of new amphipathic compounds can be used as probes for membrane studies. © 1995 Elsevier Science B.V. All rights reserved.