Background: The aim of this study was to determine learning curves for ultrasound guided transthoracic needle biopsies (US-TTNB) performed by respiratory physicians after implementation at three different centers.Methods: During January 2012 to August 2014 patients were included if they had a registered US-TTNB procedure at any of the three centers. The US-TTNB was defined as being successful if the result was diagnostic and otherwise as being unsuccessful. Histology or cytology results and clinical follow-up were used as a reference tests. The learning curves for physicians having performed at least 10 procedures were calculated using Cusum analysis. Acceptable and unacceptable failure rates were designated as being 20% and 40 respectively.Results: A total of nine respiratory physicians having performed at least 10 US-TTNB procedures were identified. The Cusum curves for each physician are depicted in figure 1. Six of the physicians had learning curves with a relatively downward or stable projection as a sign of developing competence. Three physicians, however, had learning curves with an upward projection indicating unacceptable competence in performing the procedure.Conclusion: The learning curves for US-TTNB indicate that competency in the procedure is not a given thing among respiratory physicians. Cusum score analysis could serve as a clinical tool to identify physicians needing additional training in the procedure.