OBJECTIVE: To evaluate in children microdose protocol compared with low dose for lower limb alignment (LLA) measurements on biplanar radiography. METHODS: Children 6 years or older were included. Height, weight and hip width were measured prior to imaging. Hip width allowed classifying children into morphotype M1 (width <25 cm), M2 (25-35 cm) or M3 (>35 cm) corresponding to predefined acquisition parameters (kV, mA, tube speed). Micro- and low-dose protocols were used alternately, with simultaneous acquisition of frontal and lateral radiographs. LLA measurements were performed by two independent observers (n = 526). In 15 children per morphotype, a third observer performed measurements twice (n = 180). Intraclass correlation coefficients and the dose (delivered, absorbed) were calculated. RESULTS: 100 girls and 160 boys (mean age = 11.7 years) were investigated: 74 M1 (mean BMI, 15.7kg/m222 CONCLUSIONS: Microdose could be used for LLA measurements in children and permits a significant dose reduction. CONCLUSIONS: • Lower limb lengths of children can be evaluated with microdose biplanar radiography. • Valgus/varus deviations also can be evaluated with microdose biplanar radiography. • Microdose biplanar radiography significantly reduces delivered and absorbed dose in children.