An alpha-fetoprotein (AFP) 'minigene' was constructed by joining the first two exons along with 0.9 kilobases of 5' flanking sequence of the mouse AFP gene to its last exon and 0.4 kilobases of 3' flanking sequence. This 'minigene' was tested for activity by inserting it into an SV40 vector and infecting African green monkey kidney cells. Correct initiation, termination, polyadenylation and splicing were observed. Furthermore a 220 nucleotide transcript was detected and mapped to a mouse Alu-like or B1 repeat on the opposite strand to that encoding the AFP gene in the first intervening sequence.