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The Colorado Potato beetle had been a quarantined pest in Iran until 1984. It was observed in outbreak intensities in Ardebil region in 1984. The main purpose of this research was to deliniate different aspects of the pest biology in this region. The results have indicated that the beetle has two generations annually, but since the emergence time of most of the second generation adult coincided with drying of the potato plants and sudden decline of temperature; therefore, most of them were unable to reserve enough food’. for overwintering and perished. The most viable overwinterihg beetles belonged to the first (Summer) generation. Overwintered adults emerged from the soil in early May when the temperature rose to about 12°C. Oviposition started from late May and continued until late July. Under Ardebil climatic conditions the developing periods for the first and second qenerations were 45 and 52 days respectively. Under the laboratory conditions of 20°C, 70% humidity and 12. hours light it took 41 days to develop the egg to adult. The mean rate of winter mortality was about 50%and the mean overwintering depth in Loam-Sandy Soils of Ardebil region was found to be about 12—25Cm.