delta-Crystallin is the principal structural protein of the embryonic chicken lens. In the chicken, there are two linked delta-crystallin genes arranged in the same transcriptional polarity (5'-delta 1-delta 2-3'). Here we have sequenced the delta 1 crystallin gene and almost 4.3 kilobases of its 5' flanking region. The delta 1 gene is 7766 base pairs in length and has 17 exons. At least one lariat branch consensus sequence has been identified in each intron. Analysis of the deduced delta-crystallin protein using a program which accounts for conservative amino acid changes shows regions of similarity within the delta 1 amino acid sequence. These suggest a rough 2-fold repeat in the protein structure.