AbstractExcess body weight has been identified as a risk factor for a variety of cancer types. However, whether excess body weight increases the risk of multiple myeloma remains controversial. We conducted a meta‐analysis to quantitatively summarize the evidence from epidemiologic studies of the associations of overweight and obesity with the risk of multiple myeloma. We searched the MEDLINE and EMBASE databases (1966 to May 2007) and the reference lists of retrieved articles. Cohort and case–control studies were included if they reported relative risk (RR) estimates with 95% confidence intervals (CIs) for the relation between body mass index and multiple myeloma incidence or mortality. A random‐effects model was used to combine study‐specific results. A total of 11 cohort studies (involving 13,120 cases) and 4 case–control studies (1,166 cases and 8,247 controls) were included in the meta‐analysis. Compared with individuals with normal weight, the risk of multiple myeloma was statistically significantly higher among those who were overweight (cohort studies: RR, 1.12, 95% CI, 1.07–1.18; case–control studies: RR, 1.43; 95% CI, 1.23–1.68) or obese (cohort studies: RR, 1.27, 95% CI, 1.15–1.41; case– control studies: RR, 1.82, 95% CI, 1.47–2.26). Results from this meta‐analysis indicate that excess body weight may be a risk factor for multiple myeloma. © 2007 Wiley‐Liss, Inc.