ABSTRACT. The ability of parasitic protozoan Toxoplasma gondii to change behaviour of its host is well documented. In mice, the infection causes an impaired motor performance, deficit in learning capacity and lower ability to discriminate between familiar and novel surroundings, and longer reaction times. Infected rats have higher activity levels, lower neophobia and reduced learning capacity. In human hosts, shifts in psychological profiles of the infected subjects were observed. On the other hand, there is only one study concernig the effect of infection on performance. The simple reaction time test showed that infected subjects had prolonged reaction times in comparison with Toxoplasma-free subjects.The aim of the present study is to reveal which psychomotor functions are particularly influenced by the infection. The total sample consisted of 551 conscripts (26.3 % Toxoplasma positive). Psychomotor testing was performed in Central Military Hospital, Prague, during a routine psychological session. Performance of infected and non-infected subjects in 3 series of tests was compared by ANOVA with repeating measures. Statistical analysis revealed that Toxoplasma negative subjects performed significantly better (F(1; 549) = 10.64; p=0.001) than the Toxoplasma positive ones. Because of the existence of negative correlation of IQ with the infection, this variable was added as covariate into the analysis. However, the differences in performance were still highly significant (F(1; 549) =0 8.04; p=00.005). Post hoc analyses of tests dynamics suggest that the deterioration in performance in the infected subjects is due to loss of concentration or fatigue rather than memory or learning capabilities.