Abstract: This paper reports the results of in vitro cultivation of adult Necator americanus in different media such as puppy serum, calf serum, medium 199 and Tyrode's solution. Among them, puppy serum medium and that containing a little amount of medium 1999 gave better results. 64.2% of worms survived for two weeks and 21% of them over one month in these two media. The longest survival time of female and male worms was 52 and 43 days respectively.Copulation was observed in culture medium and fertilized, and unfertilized eggs and larvae were also found.The success of in vitro culture og N. americanus has provided a new approach to study the developing stages of N. americanus and the difference between N. americanus, and Ancylostoma duodenale.