The relationship between total length (L, cm) and weight (W, kg) in the large northern pike (Esox lucius) was investigated using a dataset comprising 802 specimens weighing between 1 and 18.8 kg caught during fishing competitions. The applying the data to the equation W = aL^b, yielded a = 6.648 × 10^-6 and b = 3.0217. Weight residuals fluctuate during the fishing season, likely due to conditions of the fish, probably associated with gonad development. Additionally, the equations including maximum girth (G, cm) — W = aG^b and W = a(L × G)^b — were fitted using a subset of record fish totalling 186 specimens. Comparison of the equations W = aL^b and W = aG^b showed that weight was better described by maximum girth (AIC = 624.9) rather than by length (AIC = 690.0), but the best fit was obtained with the equation W = a(L × G)^b (AIC = 566.3) with the parameters a = 2.426 × 10^-3 and b = 0.974.