The C-reactive protein (CRP) and the erythrocyte sedimentation rate (ESR) are commonly used to assess the acute phase response. The purpose of the study is to seek the association between these two parameters. We conducted a cross-sectional retrospective. A total of 76 patients have been selected from a hospitable database. They all had a prescription of CRP and ESR. Another important inclusion criterion is the realization of blood sample for CRP and ESR on the same day and the same hour. ESR and CRP values correlated significantly with each other (Pearson r = 0.516, p < 0.001). Multiple regression analysis was therefore performed to determine the combination of variables that accounted for the greatest proportion of variance in CRP and ESR values. Neutrophils and ESR were related to CRP. Hematocrit, MCV, Albumin concentration and platelets count were significantly related to ESR the prescribers must take into account the concentrations of different parameters that influence the outcome of the CRP and ESR values directly