Germination experiments have shown that oil palm seeds require heattreatment before they germinate. The heat-treatment is in some ways analogous to low-temperature stratification of temperate seed, as it may be applied as a pretreatment, even at a moisture content too low for germination to occur. Following the heat pre-treatment, seed brought to the optimum moisture content germinates rapidly, after an initial lag period, at ambient temperature. Below a critical seed moisture content, heat-treatment is ineffective although seed viability is largely unimpaired. The high-temperature reaction has a Q10 between 3.5 and 5.0 and is apparently irreversible. Heat-treatment may be effectively applied to stored, as well as fresh, seed. A reinvestigation of the optimum temperature for the high-temperature reaction showed that dry heat-treatment is effective at 42.0°C., the duration of the treatment necessary being only 60 days compared with the previously accepted value of 80 days at 39.5°C. necessary for seed heat-treated at optimum moisture content. A temperature of 44.5°C. is rapidly fatal. These results are discussed in relation to the alternation of dry and wet seasons in West Africa, and in relation to practical aspects of oil palm cultivation.