Background Women with breast pain constitute upto 20% of breast clinic attendees. Aim: To investigate breast cancer incidence in women presenting with breast pain and establish health economics of referring women with breast pain to secondary care. Design & Setting: Prospective cohort study of all consecutive women referred to a breast diagnostic clinic over 12 months. Methods: Women were categorised by presentation into 4 distinct clinical groups and cancer incidence investigated. Results: Of 10 830 women, 1972 (18%) were referred with breast pain, 6708 (62%) with lumps, 480 (4%) with nipple symptoms,1670 (15%) with ‘other’ symptoms. Mammography, performed in 1112 women with breast pain, identified cancer in 8 (0.7%). In 1972 women with breast pain, breast cancer incidence was 0.4% compared with ~5% in each of the three other clinical groups. Using ‘breast lump’ as reference, odds ratio (OR) of women referred with breast pain having breast cancer was 0.05 (95% confidence interval 0.02–0.09; P<0.001). Compared to reassurance in primary-care, referral was more costly (net cost £262) without additional health benefits (net Quality Adjusted Life Year (QALY) loss -0.012) Greatest impact on the incremental cost effectiveness ratio (ICER) was when QALY loss due to referral associated anxiety was excluded. Primary-care reassurance no longer dominated, but the ICER remained greater (£45,528/QALY) than typical UK National Health Service cost-effectiveness thresholds. Conclusions: This study shows that referring women with breast pain to a breast diagnostic clinic is an inefficient use of limited resources. Alternative management pathways could improve capacity and reduce financial burden.