BACKGROUND: The induction of C-reactive Protein (CRP) may be attenuated by corticosteroids, whereas Procalcitonin (PCT) appears to be unaltered. We investigated, whether in community-acquired pneumonia (CAP) a combined antibiotic-corticosteroid therapy may actually lead to different slopes of decline of these inflammatory markers. PATIENTS AND METHODS: We studied the slopes of decline of PCT and CRP serum levels during 7 consecutive days as well as clinical parameters in a group of patients with CAP on or off corticosteroids. Patients with underlying COPD received systemic corticosteroids (n = 10), while non-COPD patients (n = 10) presenting with CAP alone formed the control group. All patients were treated with antibiotics. RESULTS: At baseline, relevant clinical and laboratory characteristics of the two groups were similar. Regarding the decreasing shapes of the curves from PCT and CRP, no significant differences were found (p-value = 0.48 for the groups for CRP, respectively 0.64 for PCT). All patients showed an uneventful recovery. CONCLUSION: In patients with COPD and CAP, the time courses over 7 days of PCT and CRP showed a nearly parallel decline compared to non-COPD patients with CAP. Contrary to the induction phase, corticosteroids do not modify the time-dependent decay of PCT and CRP when the underlying infectious disease (CAP) is adequately treated.