Abstract: Cloning vectors are disclosed to obtain secretion of a desired protein from a host Streptomyces when a structural gene coding for the protein is inserted into the vector. The vector has: (1) regulatory DNA that includes a promoter sequence effective to start transcription in the host Streptomyces and DNA that encodes a ribosome-binding site; (2) a DNA sequence that codes for a signal sequence that occurs naturally in a Streptomyces strain or that derives from such a DNA sequence; and (3) at least one engineered restriction endonuclease recognition site positioned for the insertion of a structural gene, the DNA that encodes a signal sequence and attached structural gene being transcribed and translated together under the control of the regulatory DNA. Expression vectors are disclosed which include a structural gene coding for a desired protein so positioned. Streptomyces cells containing the vector and methods of using them to produce the desired protein are disclosed.