Reference values for standing lumbar curvature (SLC) obtained via noninvasive methods are not well established in persons without current low back pain. The effect of gender is considered to have a significant effect on SLC with women having more lumbar lordosis than men. The effect of age and degree of obesity are not considered to have a statistically significant effect on SLC. The purpose of this study was to test the assumption that measurements of SLC in healthy adults obtained by a flexible curve will differ between genders, whereas the SLC will not differ across categories of age and body mass index (BMI). Two hundred thirty-five volunteers (119 men and 116 women) whose ages ranged between 20 and 79 years participated in the study. Subjects were almost exclusively White and from the Midwest. Measurements of the SLC were obtained by a flexible curve. The curve's shape was transferred to poster board, and the value of SLC was quantified by a previously described technique. A three-way analysis of variance (α = 0.05) was used to examine the main effects of gender, age, and BMI on SLC. The effect of gender (F_1,199 = 21.4, p < 0.0001) and the effect of age (F_5,199 = 2.8, p < 0.017) were statistically significant. The effect of BMI (F_2,199 = 1.8, p = 0.176) was not significant. Women (mean, 49.5°±10.7°) demonstrated about 6.5° more SLC than their male (mean, 43.0°±10.7°) counterparts. For age, the only significant difference was between the 20 to 29- and 50 to 59-year-old age categories. This study provides physical therapists with typical values of SLC in men and women without current low back pain.