Protein electrophoresis, hematological and cholinesterase values were determined in 32 nestling free-living peregrine falcons (Falco peregrinus) (15- to 27-days-old) in order to establish normal reference values for this population. The following values (mean +/- SD) were observed: prealbumin 0.31 +/- 0.04 g/dl, albumin 1.25 +/- 0.06 g/dl, alpha1 and alpha2-globulin 0.23 +/- 0.02 and 0.16 +/- 0.02 g/dl respectively, beta-globulin 1.02 +/- 0.05 g/dl, gamma-globulin 0.060 +/- 0.08 g/dl, total protein 3.79 +/- 0.18 g/dl, 21.26 +/- 1.30 white blood cells/microl (1 x 10(3)), 2.17 +/- 0.07 red blood cells/microl (1 x 10(6)), packed cell volume 37.58 +/- 0.82%, hemoglobin 20.96 +/- 0.29 g/dl, heterophils 61.14 +/- 2.50% and cholinesterase 1,184 +/- 75 IU/L. There were no difference in any of these parameters among males and females. The hematological values obtained could be considered as representative values in free-living nestling peregrine falcons.