Ages of Patagonian toothfish (Dissostichus eleginoides) caught off Kerguelen in 1999 were estimated by reading transverse-sectioned otoliths. Randomly interspersed otoliths from reference collections were used to measure precision; relative bias for the age data was estimated to be –0.6 years and residual variance 2.9. Age distributions of toothfish caught by two vessels showed discrepancies due to gear-specific catchability, or differences in the available population with depth or season. Age–length keys were constructed for use in assessing toothfish catches made by trawlers and longliners at Kerguelen, and longevity was estimated to be 36 years. Total instantaneous mortality Z was estimated to be between 0.09 and 0.12. Significant differences in age-at-length data between sexes were found, estimating von Bertalanffy parameters for males to be L_∞ = 95.9, K = 0.12, t₀ = –4.6 and for females L_∞ = 103.5, K = 0.11, t₀ = –4.7.