The analysis of the data on size composition of Antarctic toothfish (Dissostichus mawsoni) from catches in different statistical areas of the Ross Sea was given. Biological data for two fishery periods were selected for comparison: 2003-2005 and 2008-2012. It allowed estimating changes in the size composition of the fished part of Antarctic toothfish population. It was noted that during both periods of the fishery, in the southern statistical areas (SSRU H, I, K, L), the portion of small-sized immature fish had increased though the average size of fish in catches had not changed significantly. It may evidence to the good state of the whole population.