A 4-week drug therapy investigation in the chicken model of acute hematogeneous osteomyelitis has been performed. 105 chickens Mere divided into the following 2 control and 5 drug treated groups, with 15 chickens each group: ① the normal control, ② the experimental control, ③ the penicillin and gentamycin treated group, ④ the penicillin, gentamycin plus aspirin treated group, ⑤ the cloxacillin treated group, ⑥ the 2-week cloxacillin treated group and ⑦the cloxacillin treated group with 48 h delay. The result has shown penicillin and gentamycin, now used extensively, have poor effect on acute hematogeneous osteomyelitis caused by penicillin resistant staphylococcus aureus, whereas cloxacillin exerts far better effect. It has also been confirmed that antibiotics should be prescribed as soon as possible. Both the 2-week and 4-week cloxacillin treatments yield similar result, which supports the new idea that there is no need for a longer-than-2-3 week antibiotics treatment. It is recently suggested that prostaglandin has a special function on the development of osteomyelitis. However our experiment fails to show the effect of aspirin in osteomyelitis treatment.