The authors carried out coproscopic investigations in 20180 persons over the period of 1961-1965. It has been shown that (1) Ascaris lumbricoides infestation was relatively low (3.59 per cent) in comparison with the total worm infection (32.9 per cent) (Fig. 1), (2) there was a marked seasonal fluctuation in the occurrence of the parasite (Fig. 2), (3) there was intensified infestation of A. lumbricoides from 4 to 18 years of age.