Resumo. The cultivation of eucalyptus has become an important economic activity in Brazil. However, with the increase of the plantation areas, some entomological problems tend to increase in the same proportion. The constant monitoring of the insects associated with homogeneous planting systems is very important in order to seek the development of programs for integrated pest management. Thus, the purpose of this study was to perform a survey on the insect populations associated with Eucalyptus spp., in São Francisco de Assis, RS. The collects were carried out by light traps from July 2008 to August 2009 in three-year-old stands with the species: Eucalyptus dunni, Eucalyptus grandis and Eucalyptus grandis x Eucalyptus urophylla . The insects collected were analyzed using the faunistic indices, frequency, abundance, diversity, and constancy. The correlation between the pest species identified and the meteorological variables for the period were also performed. We collected 3623 individuals belonging to eight orders (Blattodea, Coleoptera, Dermaptera, Hemiptera, Hymenoptera, Lepidoptera, Mantodea and Odonata). Three species and three genus of lepidoptera defoliators considered of economic importance were identified: Automeris illustris, Eupseudosoma sp., Sabulodes sp., Sarsina sp., Thyrinteina arnobia and Agrotis ipsilon as well as the borer Phoracantha semipunctata . Our results show that there are important pest species of Eucalyptus already established in the region therefore some constant monitoring is required so that these species do not cause damage to plantations.