Abstract: HSP90 is a highly conserved molecule across all species, from bacteria to humans. It plays critical roles in the development, survival, chaperone function, cell cycle control, oncogenic transformation and also in response to abiotic stresses as heat or cold, or the presence of heavy metals. Little is known about biochemical and molecular responses to cold and heat stresses in entomopathogenic nematodes (EPN). In the present study, the isolation and the molecular characterization of the partial cDNA of the hsp-90 and its corresponding gene from the entomopathogenic nematode Heterorhabditis bacteriophora are reported. Four cDNA variants of the Hb-hsp-90 gene were isolated and sequenced. The unexpected finding of intron presence-absence in the Hb-hsp-90 genes of H. bacteriophora opens some questions about their function and their evolutionary significance.