BACKGROUND: Malignancies located in the upper middle mediastinum usually do not have a sufficiently large acoustic window to permit a conventional ultrasound guided parasternal biopsy. This study was concerned with an alternative approach whereby ultrasound is applied through the supraclavicular paratracheal window to allow percutaneous biopsy of middle mediastinal malignancies. METHODS: Fifteen patients who had upper mediastinal malignancies not in contact with the chest wall underwent real time and Doppler ultrasonographic studies by the supraclavicular approach. None of these tumours could be reached by conventional ultrasound guided parasternal biopsy. The ultrasound was scanned downwards through the supraclavicular fossa, along the acoustic window of the paratracheal soft tissue space. Percutaneous aspiration biopsy was performed with a 22 gauge needle under ultrasound guidance. If fine needle aspiration could not obtain an adequate tissue smear an 18 gauge Trucut biopsy was performed to obtain a histological diagnosis. RESULTS: Twelve of 15 mediastinal malignancies were detected by ultrasound through the supraclavicular approach. These 12 patients underwent percutaneous needle aspiration biopsy under ultrasound guidance. Four of the patients also had a Trucut biopsy because the needle aspirates from the tumours were inadequate. The needle had to pass through the jugular veins in four patients who received fine needle aspiration but in none of the patients who required a Trucut biopsy. Definite histological diagnoses were obtained in all 12 of these patients. Ten of the tumours were malignant and two benign. None of the patients developed any complication. CONCLUSIONS: Ultrasound and ultrasound guided biopsy through the supraclavicular paratracheal window provides a new approach for malignancy located in the upper middle mediastinum, which cannot be reached by conventional ultrasound guided parasternal biopsy. The diagnostic yield of this technique is high and the procedure is relatively safe.