During July and Aug., 1963, the feral goats in Haleakala National Park on the Island of Maul, Hawaii were studied. The number of feral goats in this park has fluctuated; It is estimated that nearly 600 goats were using the park during the summer months, 1963. Goats could enter or leave the park at any time since continuous suitable habitat for goats adjoins much of its boundary. A much larger population of feral goats occurred in the park during the 1940''s. Goats in the park did not move at random, but remained in distinct populations using certain restricted areas. Distinctly marked goats were observed to use the same ridges or palis throughout the summer. Females with young were observed to use areas no more than 0.5 min. in diameter. Populations of goats in the park were broken down into 6 areas; there seemed to be no interchange of animals between populations in these areas at this time of year. Field studies indicated that some of the populations of goats were more productive than others. Few twins were noted in the rainy portion of the park; however, twins were recorded more often in the drier areas of the crater. Breeding occurred throughout the summer; the peak period of births must have occurred in Dec. and Jan. Basic colors included black, brown, tan, buckskin, and cream. Spotted individuals were observed infrequently and none was seen that could be considered white. Dominant colors were black and brown, or variations of brown. Observations were made on the social structure of herds and herd sizes. Old billies often isolated themselves from the main groups, at least at times. Younger billies often associated with nannies and young goats. Some nannies with young also isolated themselves from the herds. Kids remained with their mother until she drove them from her. They then joined other loose flocks or attached themselves to a group of billies. Breeding was done by dominant billies that left groups of billies to join females that were receptive. Mock fighting and activity resembling play, defense, etc., were exhibited by all age groups. Feeding occurred at peak periods of activity in the midmorning and in the afternoon. When groups were actively feeding, they moved from one area to another, often trotting between bites. They sought out forbs from among clumps of grass and shrubs. Goats have increased erosion and altered plant communities. The Hawaiian flora developed without competition from ungulates, and it seems unwise to assume that feral goats could remain in the National Parks without doing much damage to native plants. Studies indicate that the goats must be eliminated from the National Park lands if these areas are to be reserved for the future peoples of the world to see native Hawaiian vegetation under as natural conditions as man can maintain. To accomplish this, the National Park lands should be fenced "goat tight" and kept in that state over the years to come. Goats can be driven from some of the areas, and in others they will have to be shot. The fencing is essential since Haleakala National Park is adjacent to and blends in with feral goat habitat on private lands. Also other ungulates have been introduced on the Hawaiian Islands and more are planned to be released for the hunting public. Fencing the park lands will help to prevent potential future probleriis created by increased populations of these new ungulates.