Larval stages of Ascaridia numidae in guinea fowls did not migrate into the liver, lungs, or other internal organs of the host. Larvae were found associated with the mucosal surface of the jejunum and ileum walls on the 4th to the 12th days of the infection by use of the Baermann technique. Before and after this period larvae located primarily in the lumen of the jejunum and ileum. Survival and development was similar in germfree and in guinea fowls which had conventional flora. The heavy parasite burden of A. numidae found in semiwild guinea fowl in Georgia has not been previously reported. Although the life cycle of Ascaridia numidae (Leiper, 1908) has recently been described as being direct (Barus, 1968; Macchioni, 1971), studies on larval tissue phases of the life cycle are incomplete. Ascaridia columbae (Wehr and Hwang, 1964) commonly invade the liver and lungs of pigeons. Two other species, Ascaridia galli (Ackert, 1931; Edgar et al., 1957) and A. dissimilis (Horton-Smith et al., 1968), rarely migrate to the visceral organs in the chicken or turkey. Disagreement is recorded on the extent and significance of larval penetration into the mucosa of the chicken (Ackert, 1923; Tugwell and Ackert, 1952; Todd and Crowdus, 1952; Moran and Mizelle, 1957; Madsen, 1962). Investigations of deep and mucosal tissue penetration of A. numidae, using new combinations of techniques, are herein reported. MATERIALS AND METHODS