The diffusion and segregation of hydrogen in surface amorphous silicon layers during solid phase epitaxy (SPE) is modeled. The SPE and H concentration profiles from J. Roth et al., Mat. Res. Soc. Symp. Proc. 205, 45 (1992) are used to test H segregation and diffusion models. Excellent agreement is obtained with a trap limited diffusion model. This model has previously been found to describe the diffusion of fluorine well. The H segregation coefficient at the crystalline-amorphous interface is determined at a temperature of 606oC to be 0.064. The possible temperature dependence of the segregation coefficient and its effect on SPE are also discussed.