In this paper, the dosimetry of small animals arranged on a monopolar patch antenna for bioelectromagnetic experiments is reported. Numerical simulations were carried out to verify the matching of the antenna in the presence of a dielectric box to accommodate the small animals. This strategy, reducing the dielectric differences between the various irradiated materials, improves largely the efficiency of the setup. The induced electric field in the biological samples reached tens of V/m for an input voltage of 1 V, which is one of the highest efficiency obtained so far for these types of exposure setup. A very short electric pulse (on-time duration of 1 ns) is transferred mostly undistorted to the biological sample guaranteeing controlled experimental exposure conditions. Optimization of the positioning of the small animals was also analyzed. Our setup can be used to study effects of short and intense electric pulses in vivo only poorly addressed so far. © 2018 Institution of Engineering and Technology.All Rights Reserved.