Proteins containing zinc finger domains have been implicated in developmental control of gene expression in Drosophila, Xenopus, mouse, and humans. Multiple cDNAs encoding zinc (II) finger structures were isolated from human cell lines of T-cell origin to explore whether zinc finger genes participate in the differentiation of human hematopoietic cells. Initial restriction analysis, genomic Southern blotting, and partial sequence comparisons revealed at least 30 nonoverlapping cDNAs designated cKox(1-30) encoding zinc finger motifs. Analysis of cKox1 demonstrated that Kox1 is a single-copy gene that is expressed in a variety of hematopoietic and nonhaematopoietic cell lines. cKox1 encodes 11 zinc fingers that were shown to bind zinc when expressed as a beta-gal-Kox1 fusion protein. Further analysis of the predicted amino acid sequence revealed a heptad repeat of leucines NH2-terminal to the finger region, which suggests a potential domain for homo- or heterodimer protein formation. On the basis of screening results it was estimated that approximately 70 zinc finger genes are expressed in human T cells. Zinc finger motifs are probably present in a large family of proteins with quite diverse and distinct functions. However, comparisons of individual finger regions in cKox1 with finger regions of cKox2 to cKox30 showed that some zinc fingers are highly conserved in their putative alpha-helical DNA binding region, supporting the notion of a zinc finger-specific DNA recognition code.