Background: The aim of this study is to evaluate the difference of clinical characteristics in patients with hyponatremia, according to the causative drugs such as thiazide diuretics and psychotropic drugs, including antidepressants (tricyclics, selective serotonin reuptake inhibitors, and monoamine oxidase inhibitors) and antipsychotic drugs (phenothiazines and butyrophenones). Methods: From 2007 to 2013, 266 patients were diagnosed with hyponatremia (P-Na <130 mmol/L). We compared clinical characteristics among thiazide (T) group (n=93), psychotropic drug (P) group (n=83), and combination (C) group (n=90). We investigated the severity of hyponatremia based on initial level of serum sodium, initial symptom of the patients and correction time (serum sodium level ≥130 mmol/L). Results: The mean age was younger in P group than in other two groups (65±8 vs 71±10 vs 74±13 year, p=0.000). There were no difference in initial urine osmolality (378±131 vs 396±154 vs 341±168 mmol/L, p=0.061) and serum osmolality (249±30 vs 244±17 vs 245±37 mmol/L, p=0.528), but serum uric acid level was significantly different among groups T, P and C (3.85±2.41 vs 2.87±1.27 vs 3.42±2.03 mg/dL, p=0.003). Serum uric acid level was higher in group T than in group P by Scheffe’s post-hoc analysis (p=0.046). All patients were divided into three categories based on the serum sodium level (mild: >125 mmol/L, moderate: 120-125 mmol/L, severe: <120 mmol/L), patient’s symptom (mild: general weakness, moderate: nausea or vomiting, severe: syncope or seizure). Incidences of severe hyponatremia and severe symptoms were not different among groups T, P and C (73.1 vs 67.5 vs 71.1 %, p=0.710, 20.4 vs 30.1 vs 17.8%, p=0.192). Correction time was significantly different among groups T, P and C (41.98±26.89 vs 34.91±23.96 vs 51.10±43.86 mg/dL, p=0.026). Correction time was longer in group C than group P by Scheffe’s post-hoc analysis (p=0.010). Conclusion: Serum sodium level and severity of symptoms were not different among groups T, P and C. Serum uric acid level was higher in group T than in group P. Correction time was longer in group C than in group P.