A mathematical model of the day to day development of the raspberry crop was constructed from estimates of the amount of fruit which ripens each day and of the rate of loss of ripe fruit as it becomes over-ripe. Efficiency characteristics of both hand and machine picking were included. The cumulative percentage of the crop harvested ripe, harvested green or lost due to natural wastage can be compared with the potential crop. This paper describes the assumptions which were necessary to set up the model, and the effects of different frequencies of hand and machine harvesting on the yield of fruit.