Objectives: The alkoxyacetic acids (AAAs) are urinary metabolites of alkoxyethanol solvents. It is well documented that these chemicals can cause acute hemolytic anemia in humans and laboratory animals. There are scarce data on the relative hemolytic activity of these acids. Likewise, information is lacking on the relationship between their hemolytic activity and physicochemical properties. The aim of this study was to compare the hemolytic activity of fi ve AAAs in red blood cells (RBCs) derived from donors' blood and male Wistar rats. Moreover, the possible relationship between lipophilic and hemolytic activity of AAAs was also investigated. Materials and Methods: The RBCs washed in TRIS buffer, pH 7.4, were adjusted to a packed cell volume (PCV) of about 20% and incubated in a water bath at 37°C for 0-3 h in the presence of different concentrations of AAAs. The hemolytic effects, in terms of the changes in RBCs, PCV, mean corpuscular volume (MCV) and free hemoglobin (HGB free ) in incubation medium, were evaluated. Based on the dose-response relationship for RBCs, PCV and MCV, the effective concentration values (EC 50 ) and their 95% confi dence intervals (95% CI) were calculated. The octanol-water partition coeffi cient (log P) and distribution coeffi cient (log D) of AAAs were computed using PALLAS software. The correlation between log P and log D values for AAAs at pH 7.4 and their EC 50 was analyzed. Results: Human RBCs were 1.9-3.1 times more resistant to the hemolytic activity of AAAs than rat erythrocytes. Also, the hemolytic activity of individual AAAs did not differ considerably; the maximum differences ranging from 2.0 to 3.3. The EC 50 values of AAAs highly correlated with their log P and log D values. Conclusions: The relatively small differences between the hemolytic effects of AAAs on rat and human erythrocytes may be associated with the strong acidity and relatively similar lipophilicity of these chemicals.