False annuli were found in 65 to 90 percent of brook trout (Salvelinus fontinalis) specimens of several year classes sampled in four Adirondack lakes. Maximum age of fish present was known since all four lakes were recently reclaimed. One or two false annuli were found on scales of trout planted as advanced fry or hatched from eggs deposited naturally. A method of identifying accessory checks based on scale measurements was developed for determining age of these trout. Influence of environmental temperature on growth rate is discussed as a possible explanation for formation of false annuli.