A 1,179 bp and a 1,424 bp full-length aryl sulfotransferase cDNAs were isolated from a human brain cDNA library. Their coding domains are 93% identical, each encoding a cytosolic protein of 295 amino acids. Their deduced amino acid sequences of these cDNAs are also 93% identical. The 1179 bp brain cDNA has an identical coding domain to a previously reported human liver aryl sulfotransferase cDNA but it has a different 5' noncoding sequence. Northern blot analysis using a probe specific for the 1,424 bp cDNA identified a 1500 bp band in mRNA of human liver, colon, kidney and lung. In a human hepatocellular carcinoma the same band plus an extra larger band was also recognised. An intron of the gene encoding the 1424 bp cDNA was also identified.