Previous studies have determined that coccidia is a common disease in pigs at days of age 7-21. The diseases causes diarrhea and inconsistent growth. There is no information about how this disease effects pigs after 21 days of age, so the total impacts of coccidia may be greater. This study tries to determine the longer term effects of coccidia on growth up to 8 weeks. To test for coccidia fecal samples were collected at 2,3 and 5 week of age from 218 randomly selected pigs on three repetitiveness farms having coccidia problems. The weights of all the test pigs and their litter mates were recorded regularly. Pigs who tested positive for coccidia at age 2-3 weeks, were 435g lighter at 4 weeks of age than pigs that tested negitively. At 5 weeks of age these pigs were 703g ligher. Coccidia infections therefore had a significantly greater impact on growth than previously thought. The current treatment methods used by veterinarians, Deccox mixed with oral iron in the creep area and single treatment of Clinacox, were proven to have no beneficial effect on growth rates.