In this study, optimization of disperse/reactive dyeing systems for resistance to the physical strength loss of Poly(lactic acid) (PLA)/cotton blended fabric was investigated. The blended fabric underwent a two-bath, two-stage dyeing process in which the PLA component of the blended fabric was dyed using two disperse dyes, followed by the cotton component being dyed with six reactive dyes containing different reactive groups dichlorotriazine, monochlorotriazine, sulphatoethylsulphone, monofluorotriazine, monochlorotriazine/sulphatoethylsulphone, and monofluorotriazine/sulphatoethylsulphone groups. The optimal dyeing systems were established according to the fixation rate of the dyes, tear/tensile strength loss, and SEM micrographs of the fabric. To avoid the strength loss during the disperse/reactive dyeing process, the recommended disperse dyeing conditions were 110 degrees C, pH 5 for 20 min, whereas the reactive dyeing conditions should be temperature <= 60 degrees C and alkali concentration <= 3 g/L. In this regard, reactive dyes containing monofluorotriazine and monofluorotriazine/sulphatoethylsulphone groups were especially suitable for the reactive dyeing systems. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 886-895, 2011