The matrix exponential exp(At) may be approximated to in some circumstances by the matrix function φp,q(At), where φp,q(u) is a Padé approximant to exp(u). The approximation breaks down if A has large latent roots, and in this case may be replaced by {φp,q(At/r)}r for some integer r. An error analysis of the latter approximation is given. A reply from the original author follows.