Objective：To investigate the infection rate of pneumocystis carinii（PC） in human immunodeficiency virus（HIV） negative immunocompromised patients in Chongqing in order to provide biological references for its early diagnosis and treatment. Methods：Sputum specimens were collected from 71 HIV-negative immunocompromised patients in Chongqing and were detected by Gomori’s methenamine silver stained（GMS） and internal transcribed spacer（ITS）-nested PCR，respectively. Results：PC was detected out in two cases out of 71 cases by GMS and PC was detected out in 25 cases by nested PCR，the difference between the two methods were significant（?字2=21.04，P=0.000） .There was no significant difference in infection rate between difference genders（ ?字2=0.375，P=0.540） and different ages（?字2=0.777，P=0.678）. The infection rates of patients with cancer，heamatolagic disorder，kidney transplantation，liver transplantation and connective tissue disease were 33.33%，26.67%，40.00%，42.86% and 39.13% respectively. There was no signifi－cant difference in infection rates between the different case groups（P=0.897）. The infection rate was significantly higher than that of abroad report and was the same as that of domestic report in 2009. Conclusion：The infection rate of PC of HIV-negative immuno－compromised patients in Chongqing is high. Clinician should enhance the alertness of patients with PC.