To evaluate the efficiency of tagging juvenile European eels with implanted 12 mm PIT tags or Eel/Lamprey Acoustic Transmitters (ELATs), we studied tag retention, survival and growth of eels (7-25 g). Experimental eels were obtained from an eel farm, tagged and then released in a series of shallow dug-out ponds with a surface area of app 200 m2 . Tagged and control eels were distributed evenly with 50 tagged and 50 control eels in each of four ponds, giving a total of 200 tagged and 200 control eels mixed. After 76 days, the ponds were drained and eels were sampled and measured. A total of 344 eels (86 %) were recaptured, indicating high survival. Tag retention was 99% as only one of the recaptured PIT- tagged eels had lost the tag and none of the ELAT tagged. The results demonstrate that tagging juvenile eels > 16 cm with these small tags is indeed feasible. The growth of tagged and control fish was differentiated but generally low in length and negative in mass, but did not differ between the three groups. This article is protected by copyright. All rights reserved.