The sweet cherry is one of the most popular of temperate fruit crops and is grown commercially in more than 40 countries around the world. The sour cherry is cultivated in fewer countries, and is used mainly in processed cherry products. Until recently, horticultural improvement of cherries as a commercial crop has been slow, and major production problems such as bird damage, rain-induced cracking, and bacterial diseases, have remained. However, in the last 30 years major developments have occurred. New improved varieties of sweet cherry have been bred which have larger fruit, are more disease resistant and set fruit more reliably. Improved sour cherry varieties have also been bred and mechanized systems of harvesting introduced. New dwarfing rootstocks are now being released.