Within 1994-2000, sections of skin collected from eleven areas on the body of 650 wild boars and 85 pigs living in the northern Poland and in the Great Poland were examined. The D. phylloides infestation in the wild boar was observed to be very heavy (prevalence 32%, mean intensity 74 ind.). In contrast, the domestic pig turned out to be free of the parasite. The wild boar D. phylloides infestations are symptomless. The parasite is relatively rare in the domestic pig, although the high animal density typical of farm stocks should aid in its spreading. Compared to that in the wild boar, the pigs affected show associated skin symptoms. Where demodicosis did occur, most often the entire population was suffering of the condition. Most probably, the wild boar is the original host of D. phylloides. The hair follicle mite in question is very frequent in the wild boar, but produces symptomless infestations. The parasite occurs more seldom in the domestic pig, but--in contrast--the infestations are much more violent.