To assess the associations between serum uric acid (SUA) level and mortality. The study included 354 110 subjects without a history of gout and whose SUA levels were tested at Chang Gung Memorial Hospital in Taiwan. Cox regression models were used to estimate hazard ratios and 95% CIs for mortality in six predefined SUA strata (≤0.17, 0.18-0.29, 0.30-0.41, 0.42-0.53, 0.54-0.65 and ≥0.66 mmol/l), after adjusting for age, sex, SUA stratum, estimated glomerular filtration rate, fasting glucose, total cholesterol and history of hypertension, diabetes mellitus, coronary heart disease, stroke, heart failure or chronic kidney disease. There were 33 562 all-cause deaths during the study period. Crude all-cause mortality rates across the SUA strata were 52.5, 19.7, 17.4, 20.0, 28.0 and 41.1 deaths per 1000 person-years. Using the stratum 3 of SUA as a reference, the age- and sex-adjusted hazard ratios (95% CIs) across SUA strata were 2.79 (2.62, 2.96), 1.32 (1.28, 1.36), 1.00, 1.10 (1.07, 1.14), 1.42 (1.37, 1.48) and 2.12 (2.01, 2.23) for all-cause mortality; 2.24 (1.93, 2.59), 1.18 (1.10, 1.27), 1.00, 1.21 (1.14, 1.29), 1.74 (1.60, 1.88) and 2.53 (2.28, 2.81) for cardiovascular mortality and 3.41 (3.11, 3.73), 1.48 (1.42, 1.55), 1.00, 0.88 (0.84, 0.92), 0.91 (0.85, 0.98) and 1.23 (1.11, 1.36) for cancer-related mortality. Individuals with SUA levels at either extremes are at higher risk for all-cause and cardiovascular mortality. SUA levels of 0.30-0.41 mmol/l were associated with the lowest mortality rate and should be regarded as optimal.