Synthetic fibers and synthetic fiber textile materials finished with mineral oil finishes, silicone oil finishes or both can be simultaneously stripped of these finishes and dyed in one liquor comprising as essential ingredients a) anionic and/or amphoteric surfactants, b) dyes, and c) optionally further compounds selected from the group consisting of the nonionic surfactants, the terpene hydrocarbons/alcohols, sorbitol esters and their alkoxylates, fatty acid ethanolamides, alkylpolyglycosides and solvents. The treatment is carried out at pH 4.0 to 7.5 at 80-110.degree. C. and at a liquor ratio of 5:1 to 100:1.