The genes encoding proteins involved in respiratory chain assembly represent candidate genes for nuclearly-encoded multiple respiratory chain deficiency. Using the long PCR amplification procedure, we have characterized the organization and complete sequence of OXA1L, a gene involved in the assembly of several complexes of the mitochondrial respiratory chain. The OXA1L gene (5 kb) is composed of 10 exons and 9 introns and contains a 24 N-terminal amino-acid stretch is characteristic of a mitochondrial presequence. The screening of OXA1L mutation in patients with multiple respiratory chain deficiency is now feasible.