Lepidopterous defoliators of Eucalyptus have caused great damage to plantations in Brazil, making it necessary to study these important insect pests. This paper presents the results of investigations of major lepidopterous (primary and secondary) pests associated with Eucalyptus plantations in nine regions in southeastern Brazil. Entomological samples were taken from Eucalyptus spp. plantations in the regions of Belo Oriente, Montes Claros, Três Marias, Alto Säo Francisco and Guanhäes (Minas Gerais State), Caçapava and Säo José dos Campos (Säo Paulo State) and Säo Mateus and Aracruz (Espírito Santo State). The insects were collected in light traps and sent to the Forest Entomology Laboratory, Animal Biology Department, Federal University of Viçosa for sorting, counting, cataloguing and identification. Eleven primary and 40 secondary pests of Eucalyptus were identified. The majority of species were in the families Saturniidae, Geometridae, Arctiidae and Notodontidae. The highest populations of insect pests, such as Thyrinteina leucoceraea and Thyrinteina arnobia (Geometridae), Eupseudosoma invluta (Arctiidae) and Glena spp. (Geometridae) were recorded during the cold and dry part of the year, from May to September. Some species, however, were present during the wet part of the year. These included Eacles imperialis magnifica, Psorocampa denticulata and Dirphia rosacordis (Notodontidae).