In this study, lung filtration coefficient (K_fc) was measured in eight isolated canine lung preparations by using three methods: standard gravimetric (Std), blood-corrected gravimetric (BC), and optical. The lungs were held in zone III conditions and were subjected to an average venous pressure increase of 8.79 ± 0.93 (mean ± SD) cmH₂O. The permeability of the lungs was increased with an infusion of alloxan (75 mg/kg). The resulting K_fc values (in milliliters · min¹ · cmH₂O¹ · 100 g dry lung weight¹) measured by using Std and BC gravimetric techniques before vs. after alloxan infusion were statistically different: Std, 0.527 ± 0.290 vs. 1.966 ± 0.283; BC, 0.313 ± 0.290 vs. 1.384 ± 0.290. However, the optical technique did not show any statistical difference between pre- and postinjury with alloxan, 0.280 ± 0.305 vs. 0.483 ± 0.297, respectively. The alloxan injury, quantified by using multiple-indicator techniques, showed an increase in permeability and a corresponding decrease in reflection coefficient for albumin (_f). Because the optical method measures the product of K_fc and _f, this study shows that albumin should not be used as an intravascular optical filtration marker when permeability is elevated. However, the optical technique, along with another means of measuring K_fc (such as BC), can be used to calculate the _f of a tracer (in this study, _f of 0.894 at baseline and 0.348 after injury). Another important finding of this study was that the ratio of baseline-to-injury K_fc values was not statistically different for Std and BC techniques, indicating that the percent contribution of slow blood-volume increases does not change because of injury.