Genetic and environmental parameters are estimated by variance analysis of numerical data obtained from two programmes of plant breeding: biparental matings and Comstock and Robinson's North Carolina Model 1. The yield component total weight of fruit bunches and its subcomponents, average bunch weight and total bunch number are considered. Two experiments, involving different families, within the structure of each design are analysed. Good agreement is reached between the findings both within and between experiments and designs, and also from character to character. Additive genetic variation appears virtually to be absent whereas dominance effects (which as notationally defined also include epistasis) are of high magnitude even in relation to the environmental contribution. This suggests that further rapid selection progress within this variety might not be immediately likely and that past selection may have caused a fixation of additive variation. However, large errors are attached to all parameter estimates. Analysis of the data year by year rather than over years indicates that there is a fall in the relative magnitude of genetic to total phenotypic variation with increasing palm age and some explanations for this phenomenon are suggested.