The safety and efficacy of the Ligasure-8 Generator with the new Ligasure V 5-mm forceps (Valleylab, Tyco Healthcare) (LS) and the Ultracision Harmonic Scalpel Generator 300 with the new 5 mm 36p Harmonic Ace forceps (Ethicon Endo-Surgery ING) (UC) are compared. Twenty New Zealand rabbits were randomly allocated into 2 groups and the short gastric vessels were divided with either LS or UC. The speed of each method, the number of the times it had to be applied, gastric perforation rates and histopathologic findings were recorded. Approximately the same number of applications was necessary for the 2 groups. UC was significantly faster but resulted in contained perforation in 3 cases against 1 for LS (difference statistically not significant). A tendency for deeper and more severe histopathologic damages was seen with UC. For routine fast dissection, UC is satisfactory, but where prevention of thermal injury is important, LS may be more appropriate.