The aim of this study was to investigate the effects of the Toxoplasma gondii infection on the total content of the essential elements Zn and Mg levels. Plasma zinc and magnesium concentrations were measured in 158 patients whose anti-T gondii IgG antibodies were positive. Scores were obtained for the patients and their age- and sex-matched 82 sero-negative healthy controls. The mean concentration of Mg in blood was significantly lower in sero-positive patients than in their controls both in females (p < 0.01) and males (p < 0.01). The average Zn concentration in seropositive female patients was 0.72+/-0.2 mg/L and 0.65+/-0.1 mg/L in controls (p > 0.05). The mean values of the Zn in blood were 1.00+/-0.3 mg/L in seropositive male patients and 0.84+/-0.2 in controls (p > 0.05). No correlation could be demonstrated between age and mean values of Zn and Mg in both sero-positive females/males and controls (p > 0.05). No significant correlation could be found between blood Zn and Mg levels in seropositive female/male patients and controls (p > 0.05). Mg levels were found to be clearly decreased in the patients with chronic toxoplasmosis, whereas no change was observed in Zn levels.