Metastasis along the needle track (NTM) after a transthoracic needle biopsy (TNB) is considered a very rare complication. A survey of the membership of the Society of Thoracic Radiology and a review of the English-language literature were conducted to assess the incidence of this complication and its predisposing factors and natural history. A questionnaire was sent to all radiology departments in the United States and Canada that had a senior member of the Society of Thoracic Radiology. The total number of TNB between 1978 and 1993 and occurrences of NTM were elicited. If an NTM was encountered, information on the size of the nodule, proximity to the pleura, histology, size of the biopsy needle, and the interval between biopsy and NTM and outcome of the patient was elicited. The incidence of NTM was estimated using binomial proportions. Results of the literature survey were tabulated to provide similar information. One hundred sixty-five questionnaires were mailed and 75 responses were received. Approximately 68,346 TNB were reported. Five departments reported a total of eight NTM, resulting in an incidence of 0.012%. The average interval between TNB and NTM was 2.6 months. There were no predictable risk factors. The outcome was known in only 11 patients; 4 patients died by the time of reporting (2 after 14 months and 1 each after 6 and 9 months). From the results of this survey, the incidence of NTM after TNB is approximately 0.012%. This small risk is random and unavoidable