In the African oil palm, Elaeis guineensis, male and female inflorescences are produced separately in an alternating cycle that is influenced by the environment: stress conditions promote male flowering, but the underlying mechanisms of this process are unknown. Adam et al. review current knowledge of sex differentiation in oil palm together with perspectives gained from other species, and suggest that at least four different types of factor can be identified that might participate in sex determination and differentiation: abiotic factors (e.g. water stress), metabolic factors (e.g. carbon reserves), hormone status and genetic factors. They present a basic framework as a step towards understanding the interactions between the various parameters of importance in oil palm sex determination.