A raspberry harvest model was constructed from smoothed values for the daily changes in berry weight with age, the daily production of ripe fruit, the rate of loss of ripe fruit with age, and the changes with ripening in fruit acidity, fruit soluble solids and harvester efficiency. The model was used to simulate the effects of harvesting the red raspberry cv. Malling Jewel at intervals of 2, 3 or 5 days, starting 4, 6, 8, 10, 12 or 14 days after the first fruits had ripened. Harvesting every 2 days was more effective with each starting time than harvesting every 3 or 5 days, because although more fruit was harvested green, less was lost through being over-ripe. In each of the 3 harvest-interval programmes the maximum amount of fruit harvested was achieved when the first harvest was delayed until 33% of the potential crop had ripened. When a theoretical one-day increase in the time that ripe berries stay on the plants before they start to fall off was used in the model, the yield of harvested fruit was increased by nearly 8% of the potential crop. The optimum combination of harvest starting time and interval between harvests removed 63.5% of the potential crop as ripe fruit.