Sixty chickens 30-55 days old with arthritis symptoms, were collected from different broiler chickens farms, all samples were examined clinically, post mortem and bacterial isolation were done. The results revealed isolation of 26 (50.98%) of Staphylococcus aureus, which were found highly sensitive to amoxycillin. The experimental infection of 10 chickens was carried out on 35 days old by intravenous inoculated with 107 cfu/ml of isolated Staphylococcus aureus. Arthritis occurred in 8 (80%) chickens. Clinical signs and post mortem findings confined to depression, swollen joints, inability to stand.