AbstractA preliminary mathematical model of fluid dynamics in acute large area burns at present incorporates plasma water, urine output, burn water loss, insensible losses via the nonburned skin, lungs, and GI tract, as well as inputs of maintenance water and therapeutic (Brooke formula) fluids. The model is an initial step in a longer‐term project to identify the pathogenetic mechanisms that control fluid shifts and to evaluate the effects of crystalloid (sodium ion), colloid (albumin), and other guidelines for fluid resuscitation. The model is initialized in homeodynamic equilibrium for a standard 70‐kg person and gives reasonable, realistic responses to a wide range of parameter variations (body sizes, burn wound loss factors), step functions (burn size, discontinuation of maintenance water), and rates of therapeutic fluid administration, given its present structure. The addition of burn and nonburn interstitial and intracellular spaces and their constituents (water, sodium, albumin, and potassium) will (1) permit validation against a wide range of clinical and experimental data, (2) suggest refinements of current resuscitation guidelines, (3) suggest more incisive research on pathogenetic mechanisms and treatment modalities, and (4) permit comparison of system dynamics with alternative modeling and simulation approac