Decomposition problems have existed since the first autopsy and persist to this day. Decomposition depends on intrinsic and extrinsic factors; temperature is the most important one.Objective: To study the medicolegal aspects of decomposition and factors affecting its occurrence in Qena and Luxor governorates. Subjects and methods: A retrospective (from 1/1/2011 to 31/12/2015), in which the decomposed cases were collected and reviewed from autopsy files, and prospective (from 1/10/2016 to 31/3/2017) study conducted in Qena Medicolegal Department (Qena and Luxor governorates), Ministry of Justice.Results: The decomposed cases in the retrospective periods ranged from (13.5 %) in 2011 to (15.7 %) in 2015 and represented (14 %) in the prospective period. Males outnumbered females, where the ratio in the retrospective periods ranged from (8.25:1) in 2013 to (2.23:1) in 2014 and represented (5:1) in the prospective period. Most cases were in the 3rd, 4th decades and full terms. Incised injuries, pathological conditions, starvation and firearm injuries were the most common causes of death, while the highest percentages of undetermined deaths were (50 %) in the retrospective periods and (33.33 %) in the prospective period. The most common sites of death were homes in 2015 (60 %) and water in the prospective period (66.67 %). The fewer layers of clothes, the more accelerated decomposition. The highest percentages of cases were found in June, 2015 (31.4 %), and in March and October of the prospective period (27.8 %).