Background: The aim was to assess the agreement between bioimpedance indices and inter-limb volume differences, as assessed by perometry, for assessment of unilateral arm lymphedema. Methods: Impedance was measured in the arms of 45 women with lymphedema and a separate control group without lymphedema (n=21). Arm volume was measured at the same time by perometry. The impedance indices, (ratio of impedances between limbs and the L-dex scores) were compared to the inter-limb volume differences using concordance correlation analysis. Results: Impedance indices were highly correlated (r=0.926) with the difference in arm volume measured by perometry. Conclusions: Bioelectrical impedance analysis, although not providing a quantitative volume measurement of lymphedema, provides a measurement index that is highly correlated with quantitative measurements of the volume increase in limb size seen in lymphedema. The speed and ease of the impedance technique renders it a suitable alternative to perometry for the assessment of lymphedema.