Serum levels of C-reactive protein as a marker of gravity of acute cholecystitis. Prospective series of cases. Acute cholecystitis (AC) is the main complication of cholelithiasis. There is evidence supporting the fact that C-reactive protein (CRP) would rise at different levels depending on severity of AC. The objective of this study was to determine the association between CRP values and clinical stages of CA severity. Series of consecutive cases of adults with AC diagnosed by clinical, ultrasound and Tokyo criteria; treated at a tertiary health center in La Paz, Bolivia between December 2019 and January 2020. The result variable was CRP determination. Others of interest were biodemographic variables. Descriptive statistics (calculation of percentages, measures of central tendency and dispersion) were applied; later, analytical statistics were applied to study the association between variables (Fisher's exact test for categorical variables and Student's t test for continuous variables). Also, 44 patients were treated (33 with mild AC and 10 with moderate AC), with an average age of 51.7±15.3 years; 59.1 % female. Average weight, height and BMI were 69.6±10.3 kg; 1.59±0.1 m; and 27±3.1 kg/m2 respectively. The mean CRP values were 9.0±11.6 and 29.5±20.2 in the mild and moderate AC subgroups respectively (p=0.001). CRP values were associated with two stages of clinical severity of Acute Cholecystitis.