Abstract. In all avocado growing countries 'Hass' is known to bear a large percentage of undersize fruit, especially as trees grow older. 'Hass' fruit of good size (i.e. > 200 g) fetches prime prices. The fact that many 'Hass' under some conditions trees produce more than 50% of their fruit with a weight less than 200 g in weight is a major drawback to this important cultivar. Preliminary data on the improvement of 'Hass' fruit size following a plant growth regulator application is presented.

'Hass' fruitlets were treated with a cytokinin in spring, 1989. At harvest, treated fruit averaged 228 g while untreated fruit averaged 180 g. No differences in fruit quality were observed between treated and untreated fruit during the postharvest inspection, in spite of the considerable increase in size of treated fruit. Large scale field trials are presently underway to follow up this first, very promising result regarding the improvement of 'Hass' fruit size by cytokinin application.