The influence of environmental conditions on fertilization and the incidence of below‑zero temperatures on fruit viability were studied in two cultivars of cherry (Prunus avium L.): "Monzón" and "De la Rosa". Pollination and fertilization observations were carried out using fluorescence microscopy. The damage induced by ice formation were determinated by observation of microscopic sections (30‑40 µm) of the ovary, previously stained with Safranine and Fast‑green. Under the environmental conditions of the experiment, fertilization rate was similar for the two cultivars studied. Two consecutive days at temperature between O and ‑2.5 °C, during 4 h, injured the ovary. The damage increased at temperatures between ‑3 and ‑6 °C during 8 h under frost temperature.