The instantaneous rate of natural mortality (M) of Champsocephalus gunnari in the South Georgia area was assessed using six different methods. Data on size composition of catches from 1964/65 to 1968/69 and the age/length key for the first half of 1972 were used in the calculations. The results provided a wide range of estimates for M. The discussion of the results suggested that M=0.56 should be used in stock assessment for C. gunnari in Subarea 48.3.