Introduction: Standing posture is controlled by the central nervous system, which relies on the recruitment of joints, ligaments, tendons, and specialized muscles to ensure minimum body oscillation and energy expenditure. Postural imbalance induces compensatory muscle contraction resulting in alteration of body biomechanics and a predisposition to early degenerative changes and overuse injuries, especially among the population practicing sports. Frequent postural screenings could detect alterations and help to prevent often life-long consequences. Objective: To assess the intra- and interobserver reliability of the spinal analysis machine (SAM), a simple portable postural screening instrument, consisting of a rectangular metal frame with bilateral electronic scales, two vertical measure tapes, and one vertical and three horizontal strings, measuring lateral body sway and the height of mastoids, shoulders and iliac crests. Subjects and methods: Participants were 21 female basketball players aged between 14 and 15 years. Measurements were conducted by two observers, and were repeated after 7 days. Statistical analysis was performed using a paired Student's t- test for repeated measures and analysis of variance (ANOVA) to assess reliability. Results: Analysis of intraobserver reliability showed no significant differences between the two measurements in any of the parameters ( P<.05). Analysis of interobserver reliability revealed a significant difference between the measurements of horizontal parameters but no significant differences between the measurements of lateral body sway and bilateral weight distribution ( P<.05). Conclusion: Given the intraobserver reliability and the relatively low cost of the SAM, this instrument could be clinically useful to screen static posture before and after therapeutic procedures. It could also be useful in longitudinal studies.