Background: For adult patients with prolonged mechanical ventilation (PMV≥7 days), weaning success is an important prognostic factor in patients requiring prolonged mechanical ventilation. Weaning failure has been attributed to various factors. The aim: of the study was to identify factors contributing to long term mechanical ventilation. A Descriptive research design was adopted to conduct this study. The study was conducted in the intensive and trauma care units at Assuit university. A convenient sample: of sixty adult male and female patients admitted to mentioned settings and connected to MV. Tools: Tool one: socio-gemograghic data and clinical data, Tool two: weaning criteria scale, Tool three APACHE II score Tool four: Neurological assessment by using FOUR score. Results: the most common risk factors delay weaning were cardiovascular (66%) and neuromuscular (54.2%). Conclusion: a highly statistically significant relation was found regarding to factors as age, length of ICU stays, RSBI, PH, hemoglobin, WBCs, platelets count and respiratory rate. Recommendations: 1-good monitoring of the cardiovascular assessment with cardiologists 2- the weaning indexes have some limitations, related to study population 3- integration with other departments should be morely supported.