Chilling accumulation infuence dormancy of grapevines and determines budbreak. Under desert conditions, hydrogen cyanamide (H2CN2) improve bud opening. To increase even further the quantity and uniformity of bud break, the effect of fall evap rative cooling (EC) alone or in combination with H2CN2(2.5%v/v was evaluated. Microsplinklers operated for 40 seconds at 10 min intervals from 10:00 h to 17:00 h, from 20 oct to 18 dec 1990. H2CN2 was applied on 21 dec, one day after pruning. Cyanamide treated plants or with the chemical + EC, had 19% and 32% budbreak, respectively, by jan 15. Control or EC vines opened until feb 20, and reached 40% and 57% final values by mar 25. Therefore, cyanamide and EC acted sinergisti cally to open buds earlier and uniformily, although not on final budbreak. Harvest started may 8 with cyanamide + EC, five days earlier than cyanamide alone; by may 13, accumulated harvest was 39% and 13% respectively, and of 92% and 77% by may 28. Control vines with or without EC, were harvested early may to mid june.