Hymenoptera is a very large and diverse insect order that includes the majority of both the social and the parasitic insects. With such diversity comes a variety and complexity of semiochemicals that reflect the varied biology of members of this order. This chapter reviews the chemical identification of pheromones and semiochemicals in the order Hymenoptera since 1990. For this review, the species in Hymenoptera have been classified as solitary, parasitic, or social. The chemical diversity of semiochemicals in Hymenoptera and future trends in pheromone identification are also discussed.