In this study, we examined the effect of alkali treatment and its variables, namely, the time (2, 4, 6, or 8 h) and the concentration of alkali (1, 5, or 17.5% w/w), on the linear density, strength, and stress-relaxation properties of jute fiber. It was demonstrated that this kind of treatment led to the creation of several voids and fiber fibrillation. Properties were measured for the alkali-treated and dewaxed fibers. The linear density and tenacity of the fibers were reduced at higher alkali concentration and at longer dipping times. The strength increased with treatment with mild alkali and decreased with treatment with the strong alkali. A very low alkali treatment (1%) rendered low relaxation. At a 5% alkali concentration, interfibrillar matrix softening also played an important role and was prominent in the stress-relaxation behavior. The stress-relaxation value was much higher in the fibers treated with 17.5% NaOH compared to the dewaxed fibers; this was probably due to a loss in the fibrillar arrangement. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 1348-1358, 2012