OBJECTIVE The bioelectrical impedance analysis method is a non-invasive, rapid accurate and practical method for assessing body composition. During last decade evidence has been gathered that supports the use of this method to monitor hydration status. This review critically examines different approaches and applications of segmental bioelectrical impedance analysis in the healthy and clinical situations. RESULTS Segmental bioelectrical impedance analysis may be useful to assess appendicular lean body mass, to estimate muscle volume and to investigate possible relationships between muscle size and strength in a limited segment of the limb. The method may become a tool for the bedside detection of fluid accumulation in critical care. CONCLUSIONS This is a review of segmental bioelectrical impedance. The preponderance of the published applications of bioelectrical impedance analysis focused on applications in a healthy population and in the field indicate the validity of the methods. A short description of the set-up of the segmental method is also given. This review discusses the application of segmental bioelectrical impedance analysis in children in different ethnic populations, in clinical situations. We also examine the application of the method to assessing body composition, and monitoring rapid changes in internal fluid balance in the field of haemodialysis and during surgery.