During the study years, the European corn borer (ECB) ( Ostrinia nubilalis Hbn.) females began depositing eggs on maize plants between the last ten days of June and the first ten days of July. A maximum number of eggs on plants was found at the beginning of the second ten days of July and at the beginning of the third ten days of July. The last egg clusters were recorded in August. During the five years of the study period, the female oviposition period lasted from 4.5 to 8 weeks. The shortest oviposition period took place during the warm and dry years, while the longest period was during the rainy and relatively cold years. During the study years, within the entire flight period, O. nubilalis females deposited from 1,564 to 3,393 eggs on 200 observed plants. The average number of eggs per cluster in the study years was from 10.0 to 15.2. The beginning of caterpillar hatching, based on the observation of empty egg clusters, was recorded in the last ten days of June or in the first and second ten days of July. Mass hatching of the caterpillars was observed in the second and third ten days of July, and only in 2004 was it in the first ten days of August. The last empty egg clusters were recorded in the second and in the third ten days of August