The use of hand rub to obtain maximum decrease in bacterial load is important because the reduction needed to avoid transmission is unknown. The monomer of 2-butanone peroxide is a peroxygen derivative with potential biocidal use in hospitals. The aim of this study was to compare the efficacy of hand rub with an alcoholic solution of peroxide 2-butanone versus five antiseptic products, against E. coli K12 (CECT 433) transient flora acquired by hand immersion in a broth culture following the UNE-EN-1500 standard. Isopropanol 60% (control) obtained 99.99% reductions, driving down the bacterial load from 10(6) cfu/mL in the initial inocula to <100 cfu/mL. Products A, B and C (different alcoholic solutions ranging from 65% to 75% with low amounts of biguanidines and/or quaternary ammonium compounds) resulted in significantly lower amounts, reducing initial inocula to approximately 500 cfu/mL. Products D and E (70-75% alcohol solutions containing higher amounts of different quaternary ammonium compounds and triclosan in the case of product E) produced reductions similar to that of isopropanol, with significantly larger reductions than products A, B and C. The product with the solution of 2-butanone peroxide produced the same effect as products D and E with mean reductions of approximately 4log(10) (99.99%), driving the initial inocula down to < or = 100 cfu/mL, despite the low concentration (35%) of propanol in the solution. This novel peroxygen biocide offers high in-vivo cidal activity against acquired E. coli transient flora, offering an alternative to products with higher alcohol concentrations.