Objective · To investigate the clinical significance of geranylgeranyl diphosphate synthase (GGPPS) by detecting its expression levels in the peripheral blood mononuclear cells of patients with acute respiratory distress syndrome (ARDS). Methods · The GGPPS mRNA expression levels in peripheral blood mononuclear cells of patients with ARDS were compared with those of healthy controls, by using quantitative reverse-transcription polymerase chain reaction. The GGPPS protein expression levels in the peripheral blood mononuclear cells were detected by Western blotting. The differential expression of GGPPS in survivors and non-survivors of ARDS was also examined. The correlations between GGPPS and clinical indicators of ARDS were tested by using Spearman’s coefficients. Results · The mRNA and protein expression levels of GGPPS in the peripheral blood mononuclear cells of patients with ARDS were significantly higher than those of healthy controls (P<0.05), and these levels increased with the aggravation of ARDS (P<0.05). Moreover, the expression levels of GGPPS mRNA and protein were significantly higher in the patients who succumbed to ARDS than those in the survivors (P<0.05). The elevated level of GGPPS mRNA was correlated with the elevated acute physiology and chronic health evaluationⅡ(APACHE Ⅱ ) score (r=0.862, P=0.000), elevated sequential organ failure assessment (SOFA) score (r=0.719, P=0.023), lower oxygenation index (r=-0.821, P=0.000), elevated C-reactive protein (r=0.758, P=0.024), and elevated white blood cells (r=0.761, P=0.015). Conclusion · The elevated expression level of GGPPS in the peripheral blood mononuclear cells is associated with greater disease severity and poorer prognosis in patients with ARDS. Based on these observations, GGPPS is expected to serve as an appropriate biomarker to assess the severity of ARDS.