Infants generally acquire HIV form mother during gestation, or delivery by contact with maternal blood and body fluids or breast feeding. At Saraburi Hospital, from January 1989 to December 1992, there were 17,766 mothers who gave birth, 80 anti HIV positive mothers were included. Up to now, four cases of PCP have been reported in HIV infants born to anti HIV positive mothers at this hospital. All cases presented with symptoms of pneumonia and bilateral bronchopneumonia by chest X-ray. Diagnosis was confirm with positive organism identification by methenamine silver stain of lung tissues autopsy, lung fluid, tracheal secretion and by toluidine blue O stain of lung percussion fluid. Two infants died before specific treatment was administered. The other two recovered with the specific treatment of trimethoprim and sulfamethoxazole. Conventional treatment was given after the definitive diagnosis was confirmed. Pediatricians should be aware of PCP. Specific treatment should be considered in infants with HIV who fail to respond to antibiotics treatment for lower respiratory infection symptoms.