Colour Doppler findings in a series of 63 cases of breast tumours and 19 cases of lymph node enlargements are reported. Colour Doppler signals of abnormal flow are found in 68.5 percent of the cancers, in 42.8 percent of metastatic lymph nodes and in 10 percent of benign lesions. There was bidirectional flow in 80 percent of all the cases. In cases of malignant tumours, the signal was correlated with the size and location of the lesions most often found peripherally. Presently, this technique appears to be of little value in determining whether a primary malignant tumour of the breast is malignant or benign. It does appear to be useful, first to follow-up cancers during initial chemotherapy (partial regression of the signal and of tumour volume) and secondly, in the diagnosis of metastatic lymph nodes with a specificity of 100 percent in our series. Colour Doppler is on the contrary difficult to interprete after conservative treatment of breast cancer because of post-radiotherapy tissue remodelling.