The pine processionary caterpillar Thaumetopoea pityocampa (Lepidoptera: Notodontidae) is considered to be a serious pest of medical importance. The hair on the dorsum of the last instar larvae of the moth may cause urticarial reactions (erucism) as well as eye problems and temporary blindness. In Israel, the pest occurs in all pine plantations as well as on ornamental pine trees in urban areas. The biology, ecology and management of the moth population are discussed as well as the mechanism of action of the urticarial hairs and their medical significance. Awareness of the life cycle and ecology of the pest may reduce the contact of the population with the urticarial hairs and prevent the morbidity caused by it.