The crop components used in a harvest model previously developed by the authors were berry weight in relation to age, rate of loss of ripe fruit, the cropping curve and fruit quality (titratable acidity and soluble solids). Measurement was for the red raspberry cultivars Malling Jewel and Glen Isla. The importance of these variables is discussed in relation to modelling raspberry crop production to compare the effects of different harvest programs on the performance of harvesters.