A series of trials was carried out with the growth hormone CERONE 720 (active ingredient ethephon) on rice (var. Rustic) in Guyana during the Autumn cycle of 1995 and Spring cycle of 1996. In 1995, (here was three experiments while in 1996 there was a larger scale on-fann experiment. The result were as follows: Experiment 1 - in which twelve CERONE 720 application rates ranging from 0 lo 51.20 g aJJL of water were administered to seed under 10 cm simulated flooded condition. The O.16-O.32g a.i./L range of treatments increased (P<0.001) seedling emergence above the flood water level 42% to 80%. The CERONE 720, therefore, increased the rate of elongation of the rice seedling leaves under flood. Experiment 2 - in which CERONE 720 was found to increase rice yield in a fanner's field by approximately 6% when applied as a seed treatment at the rate of 1.44g a.i./L of water. This trial also indicated dial a seedling rate οΓ 100 kg ha'1 could leap to a significantly (P<0.05) higher yield than (lie normal rate of 150 kg lia"1 if CERONE 720 was applied to seed at the lower seedling rale; this gave a saving of 50 kg ha"1 of seed while at the same time providing an additional 0.24 l ha"1 of grain. Experiment 3 - in which CERONE 720 was applied to experiment station plots as a foliar spray just prior to panicle initiation at the rate of 300 g a.i. ha"1. Grain yield was increased by approximately 13% while grain quality was improved. Experiment 4 - in 1996 six large scale plots were selected in four commercial farmer's field along the coastal belt of Guyana and CERONE 720 was applied at (he recommended rate of 300 g a.i. lia"1 as a foliar spray just prior to panicle initiation to one-half of each plot; the other half was untreated. The treatment led to an average increase in grain yield of 620 kg ha"1 or 12.5% of the variety Rustic which occupied about 70% of the total area under rice production in Guyana. This yield increase translated to a net profit increase οΓ approximately US$88 lia"1 (Guy $12496 ha"1) and confirmed on a large scale what was achieved on experiment station plots in the previous crop cycle.