For treatment of early breast cancer in older women, little evidence is available from randomised trials. We conducted a randomised trial comparing modified radical mastectomy (MRM) with tamoxifen (TAM) as the sole initial therapy in 164 patients aged >/=70 years with operable breast cancer. 82 were treated by MRM and 82 with TAM. Survival curves were estimated using the Kaplan-Meier method: multivariate analyses were performed using the Cox's proportional hazards model. Endpoints included survival, time to first relapse or progression, loco-regional progression, time to distant progression and progression-free survival. After a median follow-up of approximately 10 years, there was a significantly decreased time to progression in the TAM only group (logrank P<0.0001) and significantly shorter time to local progression within the TAM group (logrank P<0.0001). Overall survival of the two groups was similar. The results indicate that tamoxifen alone leads to an unacceptably high rate of local progression or relapse.