A group of 50 male Holstein-Friesian calves, 3 to 4 months old were used to evaluate a control program for gastrointestinal and hemotropic parasites. The experiment was conducted at the ICA Experimental Station in Palmira, Cauca Valley at an elevation of 1.000 m. The animals were divided into 3 groups.Twenty animals were premunized simultaneously against babesiosis and anaplasmosis; 8 days later they were treated against babesiosis using the compound 4A65 at a dosage of 1 mg./kg., of body weight, and 21 and 56 days after premunition they were treated intravenously with the compound 356-C-61 (5 mg./kg. IV) against anaplasmosis.Twenty animals were premunized against anaplasmosis as it was done with the animals in Group I. Animals in this group were vaccinated with AGS plus adjuvant vaccine against babesiosis. The vaccine was repeated 14 days later. Animals in Group I and II were treated twice during the experiment with Ripercol (Tetramisol) against gastrointestinal parasites. Ten animals were not treated and were used as controls. All three groups of calves were kept under the same environmental conditions and the same management. The experiment was carried out during a period of 8 months. Blood samples were collected to evaluate anemia and parasitemia. The antibody titer was determined by the complement fixation test. The body weights were measured and the fecal samples were examined for the presence of gastrointestinal parasites. Animals in Groups I and II had a high degree of resistance to babesiosis and anaplasmosis infections as a result of effective premunition and vaccination techniques. However, the animals in the control group had clinical babesiosis and anaplasmosis and high infestation with gastrointestinal parasites.The importance of simultaneous control of gastrointestinal and hemotropic parasites is pointed out and methods to control these parasites are given.