Abstract Early studies of the epitaxial growth of thin films were frequently largely empirical. A thermodynamic basis for interpreting growth results was the first to be developed; however, many aspects of epitaxy are governed by kinetics. Unfortunately, the kinetic phenomena are extremely complex and tools have not existed for the detailed kinetic studies required. During recent years, the difficult area of the exploration of kinetic phenomena occuring during epitaxy has progressed significantly. This paper will review significant recent advances in the areas of the kinetics of precursor reactions in the gas phase and on the surface. This will include examination of the surface structure and surface processes such as step motion, pyrolysis and atomic attachment during growth. The use of both in-situ and ex-situ tools to study these phenomena during organometallic vapor phase, molecular beam and chemical beam epitaxy will be discussed.