We report here the cDNA sequence of human hyaluronan synthase. The cDNA clone was isolated from a human fetal brain cDNA library by screening with a DNA probe generated from the coding sequence of murine hyaluronan synthase. It contains a 2107 bp cDNA insert which is composed of a 1629 bp open reading frame and a short segment of the 3'-untranslated region. Comparative analysis of the predicted coding region with the murine hyaluronan synthase sequence indicates 84.4% and 96.0% identity in nucleotide sequence and amino acid sequences, respectively. Northern analysis indicated that the gene was ubiquitously expressed in various human tissues.