Immunity can be defined as the ability of each living organism to maintain its own integrity (homeostasis) through recognizing non-self and discriminating it from self. In vertebrates innate and adaptive immunity mechanisms are involved in fighting against pathogens. According to general opinions, filogenetically older invertebrates respond to infection activating only innate immunity reactions. How-ever, a growing line of evidence indicates that the immune system in insects, crustaceans and molluscs can specifically recognize and remember infection with certain pathogens. Involvement of multiple isoforms of pattern recognition receptors containing variable Ig domains, eg. insect Dscam and snail FREPs is implicated in specific recognition of different pathogens and in selection of immune competent fagocytes. There are suggestions that invertebrates possess an alternative type of adaptive immunity functioning through mechanisms which differ from the ones known in vertebrates. The review describes new discoveries in invertebrate immunity, with special focus on insects.