Ten-year follow-up results are presented of an adjuvant clodronate trial in patients with primary breast cancer. Between 1990 and 1993, 299 women with primary node positive breast cancer were randomized to oral clodronate 1600 mg daily (149) or controls (150) for 3 years. All patients received adjuvant chemo- or endocrine therapy. Within 10 years bone metastases were detected at the same frequency in the clodronate and control groups: 44 (32%) vs. 42 (29%), respectively, (p=0.35). The frequency of non-skeletal recurrences (visceral and local) was significantly higher in the clodronate group 69 (50%) as compared with the controls 51 (36%) (p=0.005). Ten-year disease-free survival (DFS) remained significantly lower in the clodronate group (45% vs. 58%, p=0.01, respectively). This was especially seen in oestrogen receptor negative patients (25% vs. 58%, p=0.004, respectively). No significant overall survival difference was found between the groups. As previously reported 3-year adjuvant clodronate treatment did not prevent the development of bone metastases in node-positive breast cancer patients. A negative effect of clodronate on DFS by increasing the development of visceral metastases was still seen at 10 years, but this did not significantly compromise overall survival.