The electroencephalographic findings of 34 patients with toxoplasmosis were analyzed. Focal paroxysmal activity was recorded in 17 (53,1%) patients during overventilation and in 8 (24,2%) during the waking state. In normal controls focal paroxysmal activity was noted in 8 (16%) patients during overventilation, in one during the waking state and in another one during induced sleep. Fast activity was recorded in 5 (15%) patients with toxoplasmosis whereas the normal controls were free of such abnormalities. Assymetry of electrical cerebral activity was recorded in 7 (21,2%) patients with toxoplasmosis and in 3 (6%) of the normal controls. Generalised slow waves (big build-up) were recorded during overventilation in 15 (46,9%) patients with toxoplasmosis and in 11 (22%) of normal controls. Irregularity of electrical cerebral activity (moderate build-up) was noted in 12 (37,5%) patients during overventilation, and in 2 (6%) during the waking state. In normal controls, "moderate build-up" was recorded in 12 (24%) patients, and "slight build-up" in 3 (6%), always during overventilation.