This study describes the first validated model of age and growth developed for striped marlin (Kajikia audax). Daily periodicity ofotolith microincrements was corroborated by back-calculated hatch dates that matched the known spawning season in theSouthwest Pacific Ocean (SWPO). Yearly annulus formation in fin-spine sections was corroborated by daily otolith microincrementsand by a marginal increment analysis. Ages of females ranged from 140 d to 8.5 years in fish between 990 mm and 2872 mm lower-jawfork length (LJFL), and ages of males from 130 d to 7.0 years in fish between 1120 mm and 2540 mm LJFL. Sex-specific differences ingrowth were significant, with females growing to a larger asymptotic size and greater age than males. An instantaneous growth rate of3.1 mm d'1 at 6 months and an estimated length of 1422'1674 mm LJFL by age 1 year makes this species among the fastest growingbony fish. Implications of these findings are discussed in relation to commercial longline and recreational fisheries management ofstriped marlin in the SWPO and in relation to the biology of pelagic fish growth.