This study reports the nucleotide (nt) sequence of the human beta B2-crystallin (h beta B2-Cry)-encoding cDNA (h beta B2-cry). The h beta B2-cry gene encodes a major structural protein in the lens of the vertebrate eye. Sequence information obtained from mouse genomic clones and the mouse beta B2-cry cDNA (m beta B2-cry) sequence was used to design oligodeoxyribonucleotide primers, corresponding to exon 1, transcription start points, and termination and polyadenylation sites, that were used in the polymerase chain reaction (PCR) to generate full-length cDNA clones from total human lens RNA. In addition, cDNA libraries were made with lambda gt11 from both human fetal and adult lens tissue RNAs, and screened with a m beta B2-cry cDNA clone. The full-length h beta B2-cry cDNA is 721 bp and contains an open reading frame of 612 nt. It codes for a 23-kDa protein of 205 amino acid residues. Comparison of the overall nt and deduced aa sequences shows a greater similarity of h beta B2-cry to bovine beta B2-cry than to m beta B2-cry or rat beta B2-cry.