  We present examples of isospectral operators that do not have the same heat
content. Several of these examples are planar polygons that are isospectral for
the Laplace operator with Dirichlet boundary conditions. These include examples
with infinitely many components. Other planar examples have mixed Dirichlet and
Neumann boundary conditions. We also consider Schr\"{o}dinger operators acting
in $L^2[0,1]$ with Dirichlet boundary conditions, and show that an abundance of
isospectral deformations do not preserve the heat content.
