The elastic-plastic stress-strain fields in the vicinity of the notch tip of unirradiated zr-2.5 percent nb tension specimens at 250 degrees c were calculated by two-dimensional plane-strain and three-dimensional finite element analyses. the calculations support experimental work being performed in the materials integrity section at ohrd. the purpose of the calculations was to provide notch-tip stress-strain data to correlate experimental results, as well as to compare finite element results with an approximate analytical technique based on neuber's relation. incremental plasticity with isotropic material properties was used, and the load histories included unloading. for monotonic loading the notch-tip stresses were significantly lower than those calculated on an elastic basis, while the strains were significantly higher. the normal stress tangent to the notch-tip surface peaked in the interior close to the notch tip, with the distance of the peak increasing with increased plasticity. the normal strains peaked at the notch tip. the stresses in the notch-tip vicinity in the centre region of the three-dimensional models were generally close to the plane-strain results, while the three-dimensional strain results were up to 75 percent higher. after unloading, compressive stresses exceeding the yield stress occurred at the notch tip due to the residual plastic strains acting against the surrounding "unloaded" elastic material. stresses and strains at the notch tip were also calculated for monotonic loads and unloading by using an approximate analytical technique which is based on neuber's relation and deformation theory plasticity. reasonable agreement with finite element results was obtained for stresses, but the approximate analytical technique generally over-estimated notch-tip strains, by as much as 35 percent of the three-dimensional finite element results.