Cotton fabrics were dyed with three reactive dyes, C.I Reactive Blue 263, C.I Reactive Red 269, and C.I Reactive Yellow 208, after pretreatment of the fabrics with three alkyl trimethyl-ammonium bromides (tmabs) having 12, 14, and 16 carbon atoms in the alkyl chain. The pretreated samples were dyed with standard dyeing methods using conventional, reduced amounts of electrolyte, and no electrolyte. Pretreatment with the three cationics (tmabs) resulted in an increase in dye exhaustion with all dyes used, whereas total dye fixation was lower for both red and blue dye and equal for the yellow, when compared to the reference untreated samples dyed according to the same standard dyeing method. The interaction between dodecyl trimethyl-ammonium bromide and the three dyes was studied and the stoichiometry of the various dye/dodecyl trimethyl-ammonium bromide (12-tmab) complexes formed has been deduced. (C) 2008 Wiley Periodicals, Inc.