For many years, there has been a search for a set of biochemical parameters that could facilitate the assessment of severity, prognosis, and administration of early and appropriate treatment in acute pancreatitis. Administration of treatment within the first 48 hours since admission is associated with many problems of distinguishing patients with a mild form of acute pancreatitis (AP) from those with a severe form of acute pancreatitis. Study aim: To assess the relationship between the extent of change in the concentration of 10 selected biochemical indicators: amylase, lipase, total bilirubin, creatinine, uric acid, aspartate transaminase, alanine transaminase, glucose, magnesium, and iron and histopathological lesions in the pancreas within 2 and 6 hours since induction of AP. The selected time periods correspond to the first and the second day of the disease in people, respectively. Material and methods: The experiments were conducted in 110 male Wistar rats weighing from 250 to 300 g. Experimental animals were divided into three groups: Z – a group in which the ranges of the studied factors and histological structure were established; K – a group of animals operated on which were injected with 0.9% NaCl into the biliary-pancreatic duct; E – a group of animals operated on in which acute pancreatitis was induced by an injection of 5% sodium taurocholate into the biliary-pancreatic duct. Animals from the K and E groups were randomly assigned to one of five subgroups from which the material for biochemical and histological examinations was collected at 2 h and 6 h since the induction of AP. Whole pancreases were dissected for histological examinations, and the samples were dyed with hematoxylin and saturated alcoholic eosin solution. The degree of pancreatic lesions was assessed according to the Spormann score. Quantitative variables were characterized by arithmetic means, standard deviations, medians, minimum and maximum values, and 95% CIs. Results: In histological preparations from rats from the E group, after 2 hours, edematous lesions, neutrophilic infiltrations in the pancreatic parenchyma, together with single petechiae started to appear and were observed. After 6 hours, the lesions became more intense, and minor foci of coagulation necrosis and minor foci of purulent inflammation in the fatty tissue appeared. Within 2 hours, statistically significant differences in the amount of four markers: creatinine, ALT, amylase, and magnesium were observed. After six hours, statistically significant differences in the amount of two markers: AST and glucose were seen. The correlations between histological assessments according to the Spormann scale and biochemical indicators were investigated, and it was observed that within 2 hours the intensity of pancreatitis increased together with an increase in AST. In group K, within 6 hours, the intensity of inflammatory infiltration increased together with an increase in creatinine concentration (correlation coefficient 0.95; p=0.0138). In group E, in the period of 2 hours, lesion intensity in the form of inflammatory infiltration increased together with an increase in the AST level (correlation coefficient 0.90; p=0.0063) and an increase in the iron level (correlation coefficient 0.78; p=0.0399). In the same group and in the same period, an increase in the AST level (correlation coefficient 0.79; p=0.0343) was associated with an increase in lesion intensity in the form of ecchymoses. Inflammatory infiltration increased (correlation coefficient -0.87; p=0.0117) within 6 hours, whereas the creatinine level decreased. Interesting results were obtained with the use of regression analysis – forward stepwise regression. In the period of 2 hours, if the creatinine level increased by 1, the intensity of lesions in acute pancreatitis decreased by 9.02, according to the Spormann score, while the other variables remained at a stable level. However, if ALT level increased by 1, the intensity of lesions in acute pancreatitis increased by 0.02, according to the Spormann score; and if the amylase level increased by 1, the intensity of lesions in acute pancreatitis increased by 0.01, according to the Spormann score, while the other variables remained at a stable level. Conclusions: Histopathological lesions occurred prior to changes in laboratory test results, whereas significant correlations with Spormann scores were seen in the case of changes in AST and creatinine levels. The study results confirm the fact that diagnostics in acute pancreatitis is very difficult and requires monitoring of many laboratory parameters.