Two thousand one hundred and thirty five asymptomatic invasive breast cancers detected through screening mammography were analysed to identify predictors of lymph node involvement. Multivariable analysis indicated that predictors included larger tumour diameter, an infiltrating ductal or lobular histological type, multifocal disease, a palpable lesion, and a younger age at diagnosis. An association also was found between nodal involvement and the presence of an extensive in situ component (EIC). Grade was associated with nodal involvement as a univariate predictor. It would be more accurate for screening assessment clinics to use models for predicting nodal status that were customised to their own experience rather than generic models developed in other settings that related predominantly to symptomatic cancer. These models could assist clinical decision-making on axillary node dissection and give guidance to pathologists on numbers of tissue sections to examine.