The validity of scale analysis for aging tigerfish, Hydrocynus vittatus Castelnau, was assessed by examining the timing and cause of check formation on scales from fish collected in Lake Bangweulu, Zambia. Discontinuities in circuli that appeared to be valid annuli formed on all scales in September when water temperature was rising rapidly after dropping to 18 C. Spawning checks formed on scales of some fish in January. Male and female tigerfish grew at similar rates. Some females reached an age of 11 years but male tigerfish, which matured one and sometimes two years earlier, seldom lived longer than 4 years.