<jats:p>Objective: Sucrose has been used as an estimate of the extracellular fluid (ECF) volume. This study was designed to examine the hypothesis that the initial distribution volume of glucose (IDVG) correlates with the initial distribution volume of sucrose (IDVS) following volume challenges. Design: Prospective study for comparison of two methods. Setting: Animal laboratory of the University of Hirosaki School of Medicine. Materials and Methods: Ten mongrel dogs of either sex, weighing 8.5-14.0 kg, were the subject of the study. Dogs were anesthetized with pentobarbital and paralyzed with pancuronium. The volume challenge was conducted with 3% dextran in lactated Ringer’s solution 30 ml · kg^–1 over 30 min in 10 dogs. Thereafter, the same amount of the fluid was further administered in 8 of these 10 dogs. Before and after each volume challenge, glucose (100 mg·kg^–1) and sucrose (100 mg·kg^–1) were infused simultaneously over 30 s. The two estimates were calculated using a one-compartment model from repeated measurements of increased plasma glucose and sucrose during postinfusion. Results: A linear correlation was obtained between the two estimates (r = 0.89, n = 28, p< 0.0001). All dogs consistently showed that the IDVG individually followed the IDVS during changes in the latter. Conclusions: Results demonstrated that the IDVG correlated with the IDVS before and after volume changes and support the hypothesis that the IDVG is useful for evaluating the ECF volume status of highly perfused tissues.</jats:p>