Mark-resight data were analysed for 13 cohorts from a declining population of southern elephant seals branded at Macquarie Island between 1951-1965. First year survival was essentailly stable during the 1950s at c46% for females and 42% for males. There was a dramatic fall in first year survial during the 1960s, declining to <2% for both sexes in 1965. Post-year-1 survival did not change between the 1950s and the 1960s. Comparisons with a stable population of southern elephant seals at South Georgia indicated that both first year and adult survival were lower in the Macquarie Island population. There were no changes in the age at first breeding of the Macquarie Island seals during the study, but this was on average 1 yr later than at South Georgia. The current decline in elephant seal numbers at several of their major breeding islands may be due to the populations returning to pre-sealing levels after they had risen to abnormally high levels with the end of commercial exploitation early this century. -from Author