Background: Diffuse lung infiltrates pose a diagnostic challenge to the treating physician and often require diagnostic interventions. Lung biopsy is an essential tool for diagnosis, assessment and determining prognosis in different types of DPLDs. It can help to understand which subgroup of patients could benefit from current immunosuppressive treatment. Aim of the work: To demonstrate the safety, usefulness and feasibility of lung biopsy by medical thoracoscopy in patients with diffuse lung infiltrates on HRCT chest of unconfirmed diagnosis after evaluation with less invasive investigations. Subjects and methods: The study included 10 patients with diffuse lung infiltrates of unknown aetiology. They undergone full history taking, complete clinical examination, ABG analysis, HRCT chest, coagulation profile, platelet count and thoracoscopic lung biopsy by medical thoracoscopy for histopathologic examination.O2 saturation was monitored during thoracoscopy. Follow up of the patients in the inpatient unit including chest x ray for confirmation of lung expansion, observation of the intercostal tube for any complications after the procedure was done. Results: The sensitivity (No. of cases diagnosed properly) of the procedure was 90 % (9 out of 10) (ranging from 100% in malignant cases to 85.7 in non malignant cases). Good biopsy specimens obtained in all patients with average size 0.5 ×0.4 cm. Two patients (20%) had persistent air leak for 5 &7 days then resolved spontaneously. Two patients (20%) had pneumothorax after removal of the intercostal tube and resolved by supplementary high flow oxygen, six patients (60%) had pain and one patient (10%) had minor bleeding. The duration of the intercostal tube drainage was 3.1 + 2.6 days. There was no wound infection, no respiratory failure requiring ICU admission and no mortality occurred in the study sample. Conclusion: Thoracoscopic lung biopsy by medical thoracoscopy is useful in diagnosis of cases with diffuse lung infiltrates of unknown aetiology when lung biopsy is needed for accurate diagnosis. The procedure is feasible and safe. The procedure carries some complications that are not life threatening and can be minimized by good selection of patients.