Non-induced expectorated sputum (NIS) stained with tinctorial stains is not considered useful in the diagnosis of Pneumocystis carinii pneumonia (PCP). The diagnostic yield of NIS was evaluated in human immunodeficiency virus (HIV)-infected patients, when stained with a more sensitive direct fluorescent antibody for PCP-direct fluorescent antibody (PC-DFA). A retrospective analysis was carried out on fifty-five HIV-infected patients with PCP, who had NIS submitted for staining with PC-DFA. Thirty had positive NIS with PC-DFA and all had clinical courses consistent with PCP. Twenty-five had negative NIS with PC-DFA and were diagnosed as having PCP, by autopsy (n = 2), by a positive bronchoalveolar lavage (n = 10), or by having a clinical course consistent with PCP (n = 13). Thus, the sensitivity of NIS stained with PC-DFA was 55 percent (30/55). This is within the range reported in the literature for induced sputum for the diagnosis of PCP. Non-induced sputum stained with PC-DFA can be useful for the diagnosis of PCP in HIV-infected patients.