Abstract:Aim To investigate the ultrastructural changes of Pneumocystis carinii treated with dihydroarteminsinin.Methods Pneumocystis carinii pneumonia (PCP) of immuosuppressed experimental rats models were established by injection subcutaeously with cortisone acetate twice a week for 6 weeks,the PCP rats were administered orally with dihydroarteminsinin at dose of 60mg/kg once a day for 5 days.The ultructural changes of P.carinii treated with dihydroarteminsinin were investigated by transmission electronic microscope.Results It was found that the ultrastructural changes of P.carinii treaed with the arteminsin derive included formation of vacuoles in trophozoites and cysts or precysts,swelling of mitochondria and endoplasmic reticulum,rupture of nuclear membranes,rupture and dissdve of intracyst bodies.Conclusion:It suggested that dihydroarteminsinin could mainly destroy membrane system ultrastructures of P.carinii.