Field experiments conducted in 1994 (low-chill winter) and 1995 (high-chill winter) examined the effects of surfactants on the efficacy of hydrogen cyanamide (H2CN2) applied to `Perlette' grapevines (Vitis vinifera L.) in the Coachella Valley of California. In 1994, when surfactants were not used, vines treated with 1% and 2% H2CN2 exhibited similar rates of budbreak and grew more rapidly than vines treated with 0.5% H2CN2. When 1% or more of the surfactant Armobreak was used, budbreak was generally similar among all H2CN2 concentrations. The number of days after treatment required for 70% budbreak declined as H2CN2 and Armobreak concentrations were increased. Results were similar in 1995, however, budbreak was inhibited when vines were treated with 2% H2CN2 + 2% Armobreak. A separate experiment conducted in 1995 revealed that two other surfactants, Activator 90 and Agridex, had similar effects on the efficacy of H2CN2 as Armobreak. The results indicate that, when 2% surfactant is used, the standard commercial H2CN2 concentration used in California may be reduced 75% while maintaining treatment efficacy. Chemical names used: hydroxypolyoxyethylene polyoxypropylene ethyl alkylamine (Armobreak); alkyl polyoxyetheylene ether (Activator 90); paraffin petroleum oil (Agridex).