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Estimates of age and growth of flounder Paralichthys orbignyanus (Jenyns,1842) were made by analysing fish from commercial catches in Bahı´a Blanca estuary (39°LS). A total of 823 fish caught by fishing fleets operating in the estuary were collected between February 1997 and January 1998. Age was determined via scale reading and growth estimation parameters using von Bertalanffy's equation. Annulus formation occurred in August. The age for the total population, which ranged from 7.7 to 87.5 cm TL was 0-7. Age ranged from 0 to 6 years (21.5-71.9 cm TL) in males and from 0 to 7 years (24.9-87.5 cm TL) in females. Length-weight relationships were W(g) ¼ 0.0093 L(cm) exp. 3.03 for the total population, W(g) ¼ 0.0147 L(cm) exp. 2.91 for females, and W(g) ¼ 0.0168 L(cm) exp. 2.87 for males, respectively. As from age three, females were longer and heavier than males. The growth parameters estimated for the total population, for females and for males were L¥ ¼ 83.29, 79.66, and 46.11 cm, respectively; k values were 0.18, 0.23, and 0.92, respectively, and t 0 values were )1.87; )1.54, and )0.62, respectively. Similarly to other flounders, P. orbignyanus is a typical inhabitant of estuaries and coastal regions. Adults stay in the study area mainly during spring and summer, they go outside or offshore during the spawning period and then they return to the estuary for feeding and recovering.