This study was carried out to identify the infection rate of common internal parasites according to the age and the incidence of single or mixed parasitic infections from outside rearing dog in Kyungbuk province. Fifty-one dogs in 4 dog rearing farms were examined, and fece samples of dog`s were freshly collected from farm ground and rectum swabs. The results obtained from this study were summarized as follows; 1. Out of 51 dogs examined, 9 dogs were infected with some helminths, and mean infection rate was 17.6%. 2. The frequently encountered helminths were Ancylostoma caninum and Trichuris vulpis(32.3%), Toxascaris leonina(16.7%), Dipylidium caninum(8.3%) and Isospora sp(8.3%), in order. Specially the prevalence of Toxascaris leonina was relatively high in this study than other reports, and its significance was discussed. 3. The infection rate in younger dogs was higher than that of older dogs, especially that of the dogs under 6 months old was 31.3%, 6 months to 1 year old dogs was 0.8%, and over 1 year old dogs was 18.2%, respectively. 4. Single infection rates with Ancylostoma caninum, Trichuris vulpis, Toxascaris leonina, Dipylidium caninum and Isospora sp were 11.8%. But double infection rates with the Ancylostoma caninum plus Trichuris vulpis and Toxascaris leonina was 5.8%.