Three aspects of the regulation of the human alpha-skeletal actin gene are examined in this study by quantitative analysis of transgenic tissues: level of expression, tissue specificity, and developmental regulation. Previous in vitro and in vivo studies analyzing the 5' end of the gene have indicated that regulation of tissue-specific expression is promoter based. Transgenic mice were produced carrying either a 9.5-kilobase pair (kb) human alpha-skeletal actin gene fragment or a deletion construct with 2.2-kb of 5' sequences of human alpha-skeletal actin linked to the chloramphenicol acetyltransferase reporter gene. We found that the 9.5-kb transgene was capable of expression in adult skeletal muscle at a level equivalent to that of the endogenous gene in a non-transgenic mouse. The deletion construct was also capable of high-level expression. Both transgenes were expressed in a striated muscle-specific manner and were correctly regulated during development. We conclude that these three parameters of regulation of the human alpha-skeletal actin gene are mediated by sequences within the region -2000 to +239 of the promoter.