**Abstract**

The aim was to find what happens to heart weight and forms of erythrocytes antemortemly and postmortemly as a result of exposure to high water temperature. Total of 40 adult Wistar rats is divided into three groups, depending on water temperature exposure of 37°C (KG, n = 8), 41°C (G41, n = 16), and 44°C (G44, n = 16). Depending on the length of time of exposure to water, temperatures of 41 and 44°C are further divided into G41-AM, G41-PM, G44-AM, and G44-PM. The anesthetized rats were exposed to preheated water using the water bath. May-Grünwald-Giemsa coloring technique was applied to blood samples. Light microscopy was performed to detect poikilocytes. Heart weight was measured after dissection with a scale. A statistically significant difference in heart weight was found in the experimental groups (p = 0.024). The lowest value was observed in KG37 and was 0.99 ± 0.11 g, and the highest values were found in rats of the G41-PM group, with a mean value of 1.26 ± 0.26 g. There is a statistically significant difference between the experimental groups in forms of poikilocytes.

**Keywords:** poikilocytosis, antemortem, postmortem, rats, heat, heart
