A cDNA was isolated from a T cell library using an oligonucleotide probe corresponding to a sequence conserved in proteins with multiple zinc fingers of the C2H2 type. The predicted protein structure of this cDNA (ZNF43) showed that it contained 22 of the Krüppel type of zinc finger motifs in tandem. The amino acid sequence was strongly conserved between each of the finger domains of this cDNA, except for variable residue positions within the putative DNA binding site. Within the zinc finger domain the amino acid sequence of the four zinc fingers 6 to 9 was very similar to the amino acid sequence of fingers 10 to 13, the DNA sequence bound by this group of eight fingers may include a short repeat. Southern blotting showed that ZNF43 was one of a closely related family of proteins with 10 to 20 members. The members of the ZNF43 family did not appear to be clustered at the chromosomal level. The transcription of many members of this gene family was increased in lymphoid cell lines. After in vitro induced terminal differentiation of the human HL60 cell line the expression of the ZNF43 family was reduced. The expression of the ZNF43 gene was mainly limited to T and B cell lines. The gene was differentially spliced and different cell lines expressed different combinations of transcripts.