The tensile load-elongation characteristic of single papermaking fibers from wood is not readily determined on commercial load-elongation (stress-strain) apparatus because of the short length and low extension of the fibers. A new apparatus is described in which the fiber to be tested is fastened between a fixed upper grip (which may be rotated to remove fiber twist, if desired) and a lower grip attached to a pivoted beam. The fiber is strained at a constant rate of loading as a motor adds chain weight to one end of the fiber, is sensed by an electrical transducer of the variable permenance type. A recorder continuously plots the instantaneous values of load and elongation. Ranges of 0 to 30 g. load and 0 to 70mu elongation are presently accommodated. The fiber ends are gripped with glue. An epoxy resin provides the strong gripping required; but because the particular epoxy resin used appears to penetrate the fiber beyond the glue line, a more suitable material is being sought. Several actual fiber load- elongation curves are reproduced to illustrate the performance of the apparatus.