The nucleotide sequence of a 7.2-kb segment containing the mouse IL-10 (mIL-10) gene was determined. Comparison to the mIL-10 cDNA sequence (Moore, K. W., et al. 1990. Science 248:1230; 250:494) revealed the presence of five exons that span approximately 5.1 kb of genomic DNA. The noncoding regions of the mIL-10 gene contain sequences that have been associated with transcriptional regulation of several cytokine genes. The mIL-10 gene was mapped to mouse chromosome 1 and the human IL-10 gene was also mapped to human chromosome 1.