Density functional theory based on the PW91 and PBE exchange-correlation functionals was used to study processes that are expected to play a key role in single-walled carbon nanotube (SWNT) growth and continued growth. It is shown that Ni clusters adapt their shape to the shape of the SWNT end to which they are attached. The results also show that the presence of SWNTs affects Ostwald ripening of the catalyst metal clusters and that, under certain conditions, the net diffusion may be from larger to smaller clusters. Also, Ostwald ripening may affect the chiral distribution of the SWNTs.