A mouse genomic DNA fragment including the albumin gene in which central exons 9-12 had been deleted and flanked by 2.2 kb in 5' and 4.3 kb in 3' (minialbumin gene), was introduced into rat hepatoma cells and also into mouse embryos to produce transgenic mice. The minialbumin gene was specifically transcribed in stably transfected differentiated clones and a 47-k Da minialbumin was synthesized and secreted into the culture medium. In contrast, the transgene was not expressed in any of the seven independent transgenic mouse lines examined. This suggests that expression of the albumin gene in developing animals requires cis-regulating elements additional to those located within the immediate flanking regions of the gene, which are sufficient to elicit specific expression in differentiated hepatoma cells in culture.