The genes for the well-characterized high-affinity histidine transport system of S typhimurium have been cloned in lambda gt4. Genetic and physiological analyses of the analogous transport system of E coli were undertaken in order that available lambda vectors, recombinant DNA techniques, and a genetic selection for transport function might be used to isolate the Salmonella genes. The presence of the transport genes on a 12.4 Kb cloned DNA fragment has been confirmed 1) genetically, by complementation studies; 2) physiologically, by the rates of histidine uptake by bacteria containing this DNA; and 3) by demonstrating that the cloned DNA codes for the previously identified transport proteins J and P. The isolated fragment carries the entire transport operon, the argT gene and the ubiX locus, but neither the purF gene nor the ack/pta loci.