Atomic layer deposition (ALD) is poised to become one of the dominant technologies for the growth of nanometer-thick conformal films in microelectronics processing. ALD is particularly suited for the deposition of isotropic films on complex topographies under mild conditions and with monolayer control. However, many questions concerning the underlying surface chemistry need to be answered before this film deposition methodology can find widespread use. Here we highlight some recent examples of surface-science studies of ALD processes aimed to provide a basic understanding of that chemistry.