A 14-kb genomic clone containing the entire gene of human lysosomal arylsulfatase A was isolated. The arylsulfatase A gene is about 3.2 kb long and has eight exons (103-320 nucleotides in size). All intron-exon splice junctions conformed to the GT/AG consensus sequence. S1 nuclease mapping shows multiple transcription initiation sites between nucleotides -367 and -387. A fragment encompassing 360 nucleotides of the flanking sequence upstream of the transcription initiation site shows promoter activity when it was transiently expressed in COS cells using the gene for bacterial chloramphenicol acetyltransferase as a reporter gene. This putative promoter region shows four potential Sp1 binding sites but lacks typical TATA and CAAT box sequences. Three different mRNA species of 2.1, 3.7 and 4.8 kb are transcribed from the gene and arise probably from the use of different polyadenylation signals.