To elucidate the regulatory mechanism of gene expression of the human endothelin-A receptor (hET-AR), we characterized the hET-AR transcripts using reverse transcription (RT) and polymerase chain reaction (PCR) analysis in a variety of human tissues. The RT-PCR using a set of primers in exons 2 and 5 showed two lower-molecular-weight transcripts in addition to the expected fragment. PCR cloning of these two novel transcripts revealed that these transcripts contain a 199-base pair (bp) and a 327-bp deletion compared with the previously described hET-AR cDNA, respectively. Comparison of their sequences with that of the hET-AR gene showed that the lacking sequences exactly correspond to exon 4 and exons 3 and 4, respectively, suggesting that these lower-molecular-weight ET-AR transcripts may result from alternative RNA splicing. Therefore, we isolated the cDNAs of novel transcripts of hET-AR that might be generated by alternative RNA splicing. These results suggest that the alternative RNA splicing might contribute to the regulation of ET-AR gene expression.