Two series of three trioxanes and 18 disubstituted peroxides were synthesised and evaluated for their in vitro trichomonacidal activity against Trichomonas vaginalis. The most active compound, 2-methylprop-2-yl 2-methoxyeth-1-yl peroxide exhibited an IC50 value of 1.0±0.2 μM whereas other dialkyl peroxides had various IC50 values which could not be correlated to their molecule structure. The best compound was about five times more active than metronidazole. The amount of generated oxygen or free radicals cannot explain completely the activity suggesting another way of action for these compounds on T. vaginalis.