The document estimates the risk embraced by Colombian commercial banks, and establishes a measurement of excessive risk-taking that is consistent with such estimation. The construction of the excessive-risk measurement follows the basic efficient-portfolio framework, in which the variance of an aggregate portfolio is minimized subject to an observed return. Return and risk-taking in Colombia’s banking industry appear to decrease between December 2007 and May 2011. In spite of this, the excess-risk exhibits an upward trend, and denotes an increasing suboptimality when considered as a proportion of the observed risk. Hence, a reduction in the risk embraced by Colombian banks paradoxically coincides with an increase in their instability.