We prospectively investigated 30 healthy subjects with normal CD4+ T cell counts in blood and normal findings of spirometry and chest radiography for the presence of Pneumocystis jirovecii, by performing polymerase chain reaction on sputum specimens. Fifty patients with chronic obstructive pulmonary disease were investigated at the same time in the same manner; this group was used as controls for the diagnosis of pulmonary colonization with P. jirovecii. None of the healthy subjects had positive test results, whereas the fungus was detected in 8 patients with chronic obstructive pulmonary disease. The results suggest that in our region (Amiens, France), P. jirovecii is apparently uncommon in healthy subjects and that this population, therefore, plays a minor role in circulation of the fungus within human communities.