The primary aim of this study was to investigate the mechanical effects of Mulligan's "SNAG" technique on lumbar flexion ROM. The secondary aim was to measure the intra- and inter-day reliability of lumbar ROM employing the same procedure. For the interventional component of the study, 49 asymptomatic volunteers participated in it. Subjects were randomly assigned into either a treatment (SNAG) group (n=25), or a placebo (SHAM) group (n=24). The "SNAG" technique was applied on L3 and L4 spinal levels by an experienced manual therapist. SNAGs were performed with active flexion in sitting, 10 times at each level. The placebo-SHAM was similar to the SNAG without however applying the appropriate direction or force. Lumbar ROM was measured by a three dimensional electronic goniometer (Zebris CM20), before and after each technique. For the reliability component, five measurements in two different days (one week apart) were performed in 20 healthy subjects.