A total of 15 patients from 4 to 14 years of age were submitted to specific treatment for Ascaris lumbricoides infection. Seven out of these 15 patients received Levamisole (150 mg/ kg of body weight), and eight received Pyrantel Pamoate (10 mg/kg of body weight). Eggs collected directly from the uteri of the female were incubated for 18 days in H2SO4 N/10 solution. These eggs were administered per os to groups of five white mice per patient. Eight days after the infection, the mice were sacrificed to permit microscopic searching of larvae in lung specimens. Only in one out of the 75 examined mice, in the group of patients treated with Levamisole, larvae were not recovered from the lungs. Thus, it is to conclude that the drugs used in the treatment did not demonstrate deleterious effect on the A. lumbricoides eggs. However, the drugs really promote the elimination of infectious eggs. In these circumstances it is possible to believe in the in- creasing of the pollution level in communities without adequate basic sanitation facilities.