The rates of regeneration of protochlorophyll (Pchl) in leaves of dark grown seedlings of bean, pea and maize were studied, following a saturating dose of either red alone, or red followed by far red. In neither material have we found evidence for red – far red control of the initial rates of pigment regeneration. In older maize leaves, an effect was observed but only upon the final level of Pchl, reached in prolonged darkness, indicating that in this plant the rate of pigment production decreases less rapidly during the last stages of regeneration after terminal red than after far red. There is considerable pigment photobleaching in red light. It is concluded that the effect of a red pre-illumination upon the kinetics of the greening process in subsequent continuous light, is not due to a red – far red control of Pchl regeneration as such, but to a latent formative process, becoming manifest during the earlier part of a subsequent prolonged light period.