Sodium fluorescein is widely used in clinical practice for the study of the retinal circulation by angiography. It has been reported several hemorheological and microvascular abnormalities induced by this compound. The aim of this work was to analyse the hemorheological effects of intravenous sodium fluorescein in an animal model. Twenty male 10-16 weeks-old Wistar rats were used, under systemic anaesthesia. The animals were divided in 2 groups of 10 each: (1) intravenous injection of sodium fluorescein (14 mg/kg of body weight)--Group NaF, (2) controls (injection of NaCl 0.9%)--Group CTRL. A blood sample was drawn by aortic puncture after 60 minutes and hemorheological parameters determined: hematocrit, hemoglobin, metahemoglobin, carboxyhemoglobin, plasma viscosity, erythrocyte deformability, membrane fluidity and acetylcholinesterase activity. In the Group NaF there was a 20% reduction of the AChE activity (p<0.05) and an increase in PV (p<0.05). Concerning hemoglobin status, a three-fold increase in COHb (p<0.001) was shown. In conclusion, the NaF injection in the animal model produces hemorheological abnormalities similar to those reported in the human.