Cytogenetic evaluation at the time of diagnosis is essential for risk stratification in multiple myeloma, however little is known about the occurrence and prognostic significance of cytogenetic evolution during follow-up. We studied 989 patients with multiple myeloma, including 304 patients with at least two cytogenetic evaluations. Multivariable-adjusted regression models were used to assess the associations between the parameters of interest and cytogenetic evolution as well as overall survival. The prognostic significance of baseline cytogenetic abnormalities was most pronounced at the time of diagnosis and attenuated over time. In the patients with serial cytogenetic evaluations, the presence of t(11;14) at the time of diagnosis was associated with decreased odds of cytogenetic evolution during follow-up (odds ratio (OR)=0.22, 95% confidence interval (CI)=0.09-0.56, P=0.001), while the presence of at least one trisomy or tetrasomy was associated with increased odds (OR=2.96, 95% CI=1.37-6.42, P=0.006). The development of additional abnormalities during the 3 years following diagnosis was associated with increased subsequent mortality (hazard ratio=3.31, 95% CI=1.73-6.30, P<0.001). These findings emphasize the importance of the underlying clonal disease process for risk assessment and suggest that selected patients may benefit from repeated risk stratification.