The effects of mammography screening are a decrease in the sizes of tumours and a shift in stage. Very few small breast cancers (< or = 10 mm) have lymph node metastases when screening-detected, the rate being as low as 7%. Axillary clearance is not necessary for all such small tumours. A Swedish prospective cohort study, scheduled for 1500 patients, is being launched, where axillary surgery is omitted for screening-detected breast cancers of < or = 10 mm showing Elston grade I or II/and/or S-phase < or = 10%. Axillary surgery, with the associated disadvantages, will not be performed in 970 women out of 1000 expecting an axillary recurrence rate of 3%. Nordic breast cancer centres are welcome to join the study, which has already recruited around 500 patients.