Three model organic dyes (methylene blue, mordant black 11, mordant black 17) were separated from micellar solutions by cross-flow ultrafiltration at room temperature in flat modules equipped with polymeric and ceramic membranes (cut-off 15 or 50 kDa, transmembrane pressure 0.2 MPa). Cellulose acetate, polysulfone, poly(vinylidene fluoride) (PVDF) and zirconia membranes were used. The PVDF membrane was less efficient than the other ones. Sodium dode-cylsulfate (SDS), heksadecyltrimethylammonium bromide (CTAB), oxyethylated coconut fatty acid methyl esters (OMC) and binary mixtures of the ionic and nonionic surfactants were used as surfactants. The type of surfactant was the main factor affecting the retention. The highest retention coefficients (90 to 99%) were found when the ionic surfactant charged opposite to dye was used alone or in the mixture with the nonionic surfactant. For retention of mordant blacks, the CTAB or CTAB and OMC, while for retention of methylene blue the SDS were found to be the most efficient surfactants.