Percutaneous transthoracic lung biopsies are commonly performed for the investigation of lung masses. We describe current practice and complication rates in the UK. A postal questionnaire was sent to all centres in the British Thoracic Society directory. 157 replies (61% response rate) were received, providing data on 5444 biopsies. Mean number of biopsies performed per annum was 30.5 per centre; 8% of centres did not perform biopsies, 36% performed <25 biopsies per annum, 34% <50, 16% <100 and 6% >100. Consultant radiologists perform 91% of biopsies. Written consent was obtained at all centres. The operator obtained consent at 50% of centres. Written information for patients was provided at 35 (24%) centres. Biopsies are performed on a day case basis at 103 (71%) centres. Prior to biopsy the following were obtained routinely: CT scan (73% of centres), platelet count (73%), full clotting screen (70%), lung function (55%). Complications included pneumothorax (20.5% of biopsies), pneumothorax requiring chest drain (3.1%), haemoptysis (5.3%) and death (0.15%). The timing of post-procedure chest radiography was variable. Those centres that performed predominantly cutting needle biopsies had similar pneumothorax rates to centres performing mainly fine needle biopsies (18.9% vs 18.3%). There is great variation in practice throughout the UK. Most procedures are performed on a daycase basis. Small pneumothoraces are common but infrequently require treatment. National guidelines are needed to ensure consistency of standards.