Embryonic chick assay was introduced as a biological method for an experiment to apply a nanosecond pulse electric field on a tumor. Embryonic chick assay allowed many in vivo tests. Pulsed electric fields were applied on a solid tumor of the mouse breast adenocarcinoma cell, EMT6/KU, which was formed on the chorioallantoic membrane. We found that average weight of solid tumors applied pulsed electric fields was significantly smaller than that of controls.