As in most other countries, nut weevil (C nucum) is the main pest in Turkish hazelnut orchards. This insect seriously affects nut production as a direct pest. This research investigates some biological and morphological characteristics of insects and the damage they cause in three provinces in 2000 and 2001. Biological features such as adult longevity, preovipositional period, oviposition behaviour, damage types, distribution of biological stages, density and population fluctuations were determined in addition to some of the morphological characteristics of different biological stages and sex. It was observed that adults fed on leaves, while females fed on flowers and developing fruits in the early season. Damage to leaves was not serious, but significant damage due to feeding on flowers and immature nuts was observed. Insect feeding caused the fall of immature nuts and flowers. This kind of damage was as important as that made at the larval stage.