We examined variations in stage, diagnostic workup and therapy for breast cancer across Europe. Seventeen cancer registries in six European countries contributed 4,480 cases diagnosed in 1990-91. The clinical records of these cases were examined, and the distribution of stage, diagnostic examinations and therapy were analyzed. Stage was earliest in the French registries, followed by those of Italy and Eindhoven (Netherlands). The proportion of stage I cancers was highest in the French areas with screening in place. Estonia, the English registries and Granada (Spain) had the most advanced stage at diagnosis. Use of liver ultrasonography varied from 84% (Italian registries) to 18% (Granada). Bone scan use varied from 81% (Italian registries) to 15% (Mersey, UK). The highest proportions treated by breast-conserving surgery were in the French (57%) and English registries (63%); the lowest were in Estonia (6%) and Granada (11%). The highest proportions of Halsted mastectomies were in Italy (19%) and Granada (8%). In all countries except England, 90% of operations included axillary lymphadenectomy. Medical treatment only was given to 8% of (mostly advanced) cases overall. Estonia (21%) and the English registries (14%) had the highest proportions of patients given medication only. Chemotherapy was given to low proportions of node-positive cases in the Italian (76%) and English (74%) areas; breast-conserving surgery for stage I tumors varied from 24% in Granada to 84% in England. These wide differences in breast cancer care across Europe in the early 1990s indicate a need for continual monitoring of past treatments to help ensure application of the most effective protocols.