We retrospectively studied 133 patients with subarachnoid hemorrhage (SAH) to assess whether there was any gender disparity in serum electrolytes levels throughout the clinical course. Serum concentrations of sodium and potassium were measured in all patients, while catecholamines or antidiuretic hormone were assessed in a number of cases. Female SAH-patients had lower potassium level (3.29 +/- 0.47 mEq/L) than did male patients (3.68 +/-0.38) on the first day of SAH. This gender disparity continued to the beginning of the chronic phase and disappeared several months later. Mean serum sodium level was lower in the male group than in the female group throughout the clinical course. Mean serum levels of adrenaline and antidiuretic hormone were characterized by their prominent high value on the first day. Serum potassium levels were inversely related to serum levels of catecholamines, especially adrenaline, during the acute and subacute phases, particularly on the first day.