An artificial gene comprising 183 base pairs has been assembled by template-directed condensation of 35- to 53-membered oligodeoxyribo nucleotides with cyanogen bromide as a condensing agent. The reaction is complete within several minutes at 0 degrees C in buffer. The resulting mini-gene was cloned and expressed in vivo and in vitro. We have also found that the polymerase inhibition technique (toe-printing) is a good way to ascertain that translation initiation complexes form in the case of single-stranded DNAs as well. Thus, along with the fully chemical assembly of synthetic genes, a rapid and sufficiently reliable method for determining their ribosome-binding properties was developed.