Based on a detailed investigation of close-spaced vapor transport (CSVT) growth of CdTe, a diffusion-limited transport model is proposed. Excellent quantitative agreement between the experimental data and the diffusion model supports its applicability. Surface temperatures used in the diffusion model are calculated from a one-dimensional thermal analysis of the CSVT system that includes conductive, radiative, and convective heat transfer. Comparison between growths in He and H2 reveals that H2 does not enhance the growth rate by acting as a chemical transport agent, although small deviations from diffusion-limited growth in H2 are attributed to H2Te formation. An equilibrium thermodynamic analysis of the H2, H2Te, Te2, Cd, and CdTe system supports this hypothesis.