Many factors involved in wound healing can stimulate tumour growth in the experimental setting. This study examined the relationship between wound complications and the development of systemic recurrence after treatment of primary breast cancer. One thousand and sixty-five patients diagnosed with operable primary invasive breast cancer between 1994 and 2001 were assessed for development of systemic recurrence according to whether or not a wound complication occurred after surgery, with a median follow-up of 54 months (range 15-119). There were 93 wound complications (9%). There was a statistically significant greater risk of developing systemic recurrence in patients with wound problems than those without (hazard ratio (HR) 2.87; 95% CI: 1.97, 4.18; P<0.0001). This remained in a multivariate analysis after adjustment for case mix variables, including Nottingham Prognostic Index (NPI) and oestrogen-progesterone receptor status (HR: 2.52; 95% CI: 1.69, 3.77; P<0.0001). In the good prognostic NPI group, 4 out of 27 patients (15%) with wound problems vs 11 out of 334 (3%) without wound problems developed systemic recurrence. The corresponding figures were 10 out of 35 (29%) vs 48 out of 412 (12 %) in the moderate prognostic group and 18 out of 29 (62%) vs 75 out of 199 (38%) in the poor prognostic group. In 29 patients NPI could not be calculated. Smokers at the time of diagnosis were more likely to develop metastatic disease than the non-smokers (HR: 1.50; 95% CI: 1.04, 2.15; P=0.03) after adjustment for other factors. The results suggest that patients with wound complications at primary surgery have increased rates of systemic recurrence of breast cancer.