Age estimates of mackerel icefish from different laboratories obtained during a CCAMLR ototlith exchange programme in the late 1980’s revealed considerable differences between readers when fish older than 3 or 4 years were aged. These differences could not be reconciled at the end of the exchange. A second age determination workshop on mackerel icefish to improve the accuracy of age determination was agreed upon at the last meeting of the ‘Working Group on Fish Stock Assessment’. Our report briefly summarizes the state of knowledge on age determination in mackerel icefish and assesses the validity of ageing. Possible ways forward were described to improve the validity of age determinations of the species.