Four different forms of jute fibers, namely untreated jute filament (UJF), sliver jute filament (SJF), bleached jute filament (BJF), and mercerized jute filament (MJF), have been subjected to tensile strength analysis following Weibull＇s theory. The MJF and BJF were obtained by the chemical modification of the UJF. A minimum of 50 fibers of each type, at three different gauge lengths, i.e., 15, 30, and 50 mm, were used to study the strength distribution and the effect of gauge length. The mean fiber strength was found to be the maximum for UJF followed, in the order, by BJF, MJF, and SJF (similar to 700, similar to 660, similar to 580, and similar to 540 MPa, respectively, at 50-mm gauge length). The strength was also found to decrease with an increase in gauge length. In all cases, good agreement was found with Weibull＇s statistical model. Single fiber composite tests, with an epoxy resin as the matrix, were carried out determine the critical fragment lengths and interfacial strength, following the Kelly-Tyson approach. The BJF was found to have the maximum interfacial adhesion (tau approximate to 140 MPa) followed by UJF, SJF, and MJF having tau values of similar to 83, similar to 57, and similar to 47 MPa, respectively. Scanning electron microscope pictures showed the fiber surface was physically modified by the various treatments. (C) 2000 John Wiley & Sons, Inc.