Abstract The chaperonins are evolutionarily conserved essential cellular proteins that help folding newly synthesized or translocated proteins, spending ATP. We present here the molecular analysis of the hsp60 gene promoter region and of two Drosophila hsp60 ethyl methane sulfonate embryonic lethal alleles that have an identical phenotype. No heat shock element sequences were found in the 5′ region, supporting previous data (Kozlova, T. et al., 1997) which suggests that mitochondrial Drosophila melanogaster HSP60.1 is not heat inducible. By sequencing the lethal allele’s entire open reading frame (ORF), we found a C-T transition in the hsp60 F409 allele that produces a serine to leucine change, apparently distorting the protein equatorial domain structure. No changes were found in the hsp60 G93 ORF. However, an analysis of the heterogeneous nuclear RNA levels showed a reduction of the hsp60 transcript in hsp60 G93 flies as compared to the wild-type. These data suggest that although the defects in the hsp60 gene produced by these alleles are at different levels, both behave as null mutations.