The body fluid changes of 12 burn patients treated with Hypertonic Lactate Saline solution (HLS group) were compared with 26 burn patients receiving isotonic therapy (iso Na group).Total infusion volume during the first 48 hours postburn in the HLS group was only one-half to two-thirds of that in the iso Na group, although the sodium loads were nearly equal.HLS therapy maintained sufficient functional extracellular fluid volume (f-ECFV) in the shock period and protected the excess increase of f-ECFV in the postresuscitative period, in contradistinction to the iso Na group.In this paper, some clinical problems such as a rapid shift of ECF water into the ICF space and hypernatremia following HLS administration are discussed.