In general, differences in personality factors were greater in subjects in older age groups. In order to ascertain whether there was any correlation between personality change and duration of infection, personality test (16PF) data were available on 190 men and 230 women in whom acute toxoplasmosis had been diagnosed in the previous 14 years. After the age of subjects was controlled for, superego strength (factor G) was found to significantly decrease in men (P = 0.017, t-test, 1 tailed)3 and increase in women (P = 0.010, t-test, 1 tailed)6 in relation to the duration of infection.