Pneumocystis jirovecii pneumonia (PCP) is emerging in HIV-negative patients, for whom the prognosis is significantly worse than in HIV-infected patients and risk factors are poorly characterized. We performed an observational, multi-centre, prospective study of 56 consecutive cases of documented PCP in HIV-negative patients, and found that: (1) the main underlying conditions were haematological malignancies (43%), solid tumours (25%), inflammatory diseases (20%), and solid organ transplantation (7%); (2) most patients (80%) had received prolonged corticosteroids, with a mean daily dose of 47.3 ± 32.8 mg equivalent prednisone when PCP was diagnosed, and a mean cumulative dose of 5807 ± 5048 mg over the last 12 months; and (3) the median CD4 cell count was 0.12 × 10⁹/l (range 0.0-1.42), with a median CD4/CD8 ratio of 1.32 (0.0-6.4). These findings may be used to better target PCP prophylaxis according to the level of risk and contribute to decrease the burden of PCP in HIV-negative patients.