  We present a calculation of the rational terms in two-loop all-plus gluon
amplitudes using $D$-dimensional unitarity. We use a conjecture of separability
of the two loops, and then a simple generalization of one-loop $D$-dimensional
unitarity to perform calculations. We compute the four- and five-point rational
terms analytically, and the six- and seven-point ones numerically. We find
agreement with previous calculations of Dalgleish, Dunbar, Godwin, Jehu,
Perkins, and Strong. For a special subleading-color amplitude, we compute the
eight- and nine-point results numerically, and find agreement with an all-$n$
conjecture of Dunbar, Perkins, and Strong.
