Abstract: A total of 106 juveniles of A. duodenale about 2mm long with undeveloped genital organs secured on the 14th day from intestine of experimentally infected puppies were cultured in dog serum and 50% dog serum + 50 % RPMI 1640 medium. 90% of juveniles survived well and many of them grew to sexual maturity. The earliest oviposition stage observed was at the 24th day after cultivation in vitro. The maximum number of eggs laid per day amounted to 7 000. The longest duration of the worm survival was 154 days, reaching 8-9mm in length. Two pairs of worms matured in the culture plate copulated. Fertilized eggs were oviposited after copulation, and a great number of infective larvae were obtained. 436 adult A. duodenale were recovered from puppies artificially reinfected with these infective larvae (Plates 1-4).