Background: Impaired cough increases risk of reintubation in patients who pass a spontaneous breathing trial and have their endotracheal tube removed .Semi-quantitative cough strength score (SCSS) used to evaluate the patients’ cough strength which was scored from 0 to 5 according to the obtained patient response Aim: to evaluate factors affecting extubation outcome by using (SCSS) Design: descriptive design. Setting: intensive care units of anesthesia department at assuit university hospital. Subjects: convenient sample of 80 patients who were ready for weaning off mechanical ventilator, aged from 18-65 years old, mechanically ventilated more than 24hours and of Glasgow coma scale (GCS) of 12-15. Tools: Tool I Assessment sheet. Tool II: SCSS Tool III: factors affecting extubation outcome assessment sheet Method: Before extubation, patients positioned at 30° to 45°, SCSS was measured by asking patient to cough using his full power, then disconnecting him from the ventilator. Results: 80% of the patients with (grade =0) reintubated in comparison with 79% of patients with (grade =5) successfully extubated. Conclusion: The most common factors affecting extubation were copious secretions, diminished consciousness, hypoxemia and anemia respectively.