We evaluated the additional benefit of Technetium99-sestamibi (99mTc-MIBI) scanning in comparison with standard X-ray techniques for multiple myeloma patients either at diagnosis or during follow-up. Between February 2001 and January 2005, 397 whole body scans were acquired. On 229 scans performed at diagnosis, 146 (64%) were positive and 81 cases have discordant X-ray results. The sensitivity of 99mTc-MIBI and X-ray were 77% and 45% respectively. As a result of 99mTc-MIBI, 40% of asymptomatic myeloma patients were up-staged. The positivity of 99mTc-MIBI correlated significantly with all of the most relevant clinical and biological parameters. Multivariate analysis selected only high reactive C protein (P = 0·0005), bone marrow infiltration (P = 0·02) and bone pain (P = 0·002) as factors affecting 99mTc-MIBI pattern. In 22 patients with solitary myeloma, 99mTc-MIBI was positive in 86% of cases and detected more disease sites than X-ray. Among 168 scans performed during follow-up, 99mTc-MIBI presented high specificity in patients showing a complete response (CR; 86%), and correlated with myeloma activity and with response to therapy. At multivariate analysis, a positive pattern correlated with bone marrow infiltration (P = 0·002) and disease status other than CR (P = 0·03). We conclude that 99mTc-MIBI scanning is an additional diagnostic tool with a high specificity for the staging and the follow-up of multiple myeloma patients.