We report seven women, aged 52-78 years, with motor neuron disease (MND) associated with breast cancer. In five, cancer preceded MND by 30 years to 24 months, while in the remaining two it occurred from 8.5 years to one month after MND onset. Three patients were considered cured of their cancer at the time of the study. Four patients have died, one from associated colonic cancer, and three from MND. As in a previous report, the clinical pattern of MND in these patients was that of predominant upper motor neuron involvement in 6/7 cases. Three had frontotemporal dementia. No anti-neuronal antibodies were found. Although there is no recognized pathophysiological link between breast cancer and UMN-predominant MND we suggest there may be comorbidity between the two diseases.