A case of a primary pulmonary leiomyosarcoma originating in the right pulmonary artery in a 61-year-old woman is reported. Patient's complaints were non-specific and after non-invasive diagnostics a chronic thromboembolic event was suspected to have occurred a long time ago. During a heart catheter investigation prior to planned surgical embolectomy a small specimen was taken from the pulmonary artery. Histological examination revealed malignant the tumour and by immunohistological staining its smooth muscle differentiation was confirmed. Complete resection of the tumour was achieved by radical surgery, including pneumonectomy and extensive resection of pulmonary vessels with subsequent implantation of a Goretex prosthetic. There was no evidence of recurrence or metastasis of the primary leiomyosarcoma of the pulmonary artery in a 14-month follow-up period after operation.