In various contexts, several mathematicians have discovered a binomial theorem of the following form: Let T1,T2 be complex matrices such that T2T1 = qT1T2. Then (T1 + T2)n = SIGMA(k = 0)n alpha(n,k)(q)T1(k)T2n-k and the polynomials alpha(n,k)(q) are given explicitly. We describe an application of this result in our work on matrices whose eigenvalues have certain symmetries.