Weight-length data from 51 brown troutSalmo truttapopulations (N= 10,673) in 14 states and one Canadian province were used to develop a standard weight (Ws) equation for stream-dwelling brown trout. The regression-line-percentile technique was used to develop theWsequation from weight-length regressions for individual brown trout populations. The proposed Ws. equation is log10Ws(g) = −4.867 + 2.960 log10TL (mm), and the English equivalent is log10Ws(lb) = −3.366 + 2.960 log10TL (in). This equation is valid for fish 140 mm (approximately 6 in) and longer. Benchmark length categories were established using percentages applied to the largest individual of the data set. Proposed length category standards are 150 mm (6 in), 230 mm (9 in), 300 mm (12 in), 380 mm (15 in), and 460 mm (18 in) for stock, quality, preferred, memorable, and trophy lengths, respectively.