A parasitological examination realized on the white horse herd in district of Thanh Tri, Ha noi city indicated that were infected by 6 parasite species at different prevalence i.e. Anoplocephala spp. 2.47 percent, Parascaris equorum 30.86 percent, Strongylus spp. 44.44 percent, Trichonema spp. 25.93 percent, Strongyloides westeri 6.17 percent, Dictyocaulus amfield 22.22 percent and Oxyuris equi 28.39 percent. The highest prevalence was found in the 3-12 month old animals. The prevalence of 100 percent with an intensity if infection of 576 + or - 79.7 eggs/gram of excrement was found in the time period of September-October and the lowest prevalence (75.30 percent, at an intensity of 235 = or - 38.7 eggs/gram) was registered in the period July - August. The results of deworming indicated that ivermectin, s/c, reduced by 90.91 percent to 95.66 percent the number of eggs per gram of the excrement and 66.67 percent of the treated animals showed no more ova in stool. Likewise, the treatment by levamisole, i/m. gave the folowing figures: 80.16 percent to 86.34 percent and 33.33 percent, respectively. The Ivermectin dosis was 0.3 mg/kg LW for the young horses and 0.2 mg/kg LW for the grower horses.