The objective of this study is to investigate the clinical markers of life-threatening Pneumocystis pneumonia (PCP) in patients with collagen vascular diseases (CVD). The patients who contracted Pneumocystis jeroveccii were retrospectively selected from our medical charts and conditions related to the patients' death were reviewed. The findings indicated that lower levels of serum albumin and cholinesterase, increased alveolar-arterial oxygen gradient, intratracheal intubation, and necessity to treat in the intensive care unit were significantly related to deaths associated with PCP in CVD. A special attention should be paid to decreased serum albumin and cholinesterase as ominous predictors in PCP occurred in patients with CVD.