String theory on AdS_3 x S^3 x T^4 has 20 moduli. I will discuss how the perturbative closed string spectrum changes as we move around this moduli space in both the RR and NSNS flux backgrounds. At weak string coupling, only four of the moduli affect the energies. In the RR background the only effect of these moduli is to change the radius of curvature of the background. On the other hand, in the NSNS background, the moduli introduce worldsheet interactions which enable the use of integrability methods to solve the spectral problem. These results show that the worldsheet theory is integrable across the 20 dimensional moduli space.
