In this paper we characterize the human carboxyl ester lipase-like (CELL) transcript. An analysis of the tissue distribution of the expression of the gene shows that it is expressed in low amounts in all tissues analyzed. This is in contrast to its closely related and functional gene, the carboxyl ester lipase (CEL) gene, which is expressed only in human lactating mammary gland and pancreas. The primary structure of the cDNA encoding the carboxyl ester lipase-like transcript has been determined. The average length of the cDNA is 1214 bases. This sequence includes several termination codons in all three reading frames. The longest open reading frame with the same start of translation as that of the CEL transcript could encode a 59-amino-acid-long peptide, presumably without any function. The CELL gene may have arisen as a result of a gene duplication of the CEL gene followed by deletions and point mutations. However, the mutations are unevenly distributed. In the first three exons no mutations are found compared to the corresponding exons of the CEL gene. On the other hand, in the next exon several point mutations and a 2-base insertion are found and are present in all individuals analyzed. A hypervariable region present in the last exon of the CELL gene is also characterized. Several allelic variants can be resolved by polymerase chain reaction amplification of this region followed by sequencing using an automated laser fluorescent sequencer.(ABSTRACT TRUNCATED AT 250 WORDS)