A 147-bp cDNA fragment was isolated from human lymphocytes activated with concanavalin A using the method of direct selection. A complete copy of the selected gene having total homology with the mitochondrial ribosomal gene MRPL37 was obtained by the RACE (rapid amplification of cDNA ends) technique. The MRPL37 gene was localized on human chromosome 1 using a DNA panel composed of somatic cellular human-hamster hybrids. The Northern blotting and RT-PCR (reverse transcription-polymerase chain reaction) demonstrated that the RNA of the human MRPL37 gene is widely represented in the lymphoma populations of Raji B cells and MT4 T cells, as well as in pancreas, liver, and lung embryonic fibroblasts WI-38 and LEH. The highest expression level of the MRPL37 mouse homologue was found in the cells of skeletal muscles, the heart, and organs of reproductive system: the uterus, ovaries, and testicles. A comparative analysis of the MRPL37 amino acid sequence with those of proteins represented in the Fasta33 and GenBank databases showed a homologous region in MRPL37 and PDCD9 (programmed cell death 9, MPRS30) proteins. The chicken homologue of PDCD9 is interesting because its overexpression causes apoptosis of the mouse fibroblasts C3H10T1/2. The existence of a common domain indicates possible similar functional peculiarities of the PDCD9 and MRPL37 genes and may imply the MRPL37 involvement in the process of apoptosis. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2004, vol. 30, no. 5; see also http: // www.maik.ru.